This build is not a catalog chassis job. A slammed long-bed C20 with a Duramax, Allison, 22-inch wheels, and 8-lug hardware changes everything: engine clearance, steering path, exhaust routing, frame width, suspension geometry, and wheel fitment. The real challenge is packaging all of that without building a truck that only looks right parked. The chassis plan starts with a full 3D scan of the truck so the frame, suspension, and drivetrain can be laid out around the body instead of guessed at. From there, the focus is strength and control. The long wheelbase and diesel torque call for a stiffer center section, more gusseting, and careful motor-mount compliance so the engine stays planted without making the truck miserable to drive. At the same time, the front geometry, track width, and wheel position have to work with 22s, air ride, and full tuck while still keeping turning radius and real street use intact. The 8-lug requirement is its own problem, which means custom spindle and rear axle work instead of standard hot-rod hardware. That is what this build comes down to: making the stance, the diesel package, and the drivability all live in the same truck.
Gale Banks and the team traveled roughly 2,000 miles to Mundelein, Illinois, to meet with Roadster Shop as they began planning a custom chassis for Lockjaw, their heavily modified truck project. The visit centered on whether Roadster Shop could build a chassis for an unusual combination: a slammed long-bed C20 running a large Duramax diesel, an Allison transmission, oversized wheels, and extensive custom hardware.
Josh from Roadster Shop explained that the company's current scope grew significantly after Neil, Phil, and Jeremy Gerber purchased the business in 2004. What had been a respected local hot rod shop evolved into a much larger operation known not only for chassis manufacturing but also for complete vehicle builds. Early showcase cars helped demonstrate the company's capabilities, and that momentum expanded into a full-scale engineering, fabrication, and production business.
Roadster Shop's reputation was built on more than attractive finished vehicles. According to the team, the real differentiator was the engineering and production system behind them. Walking through the facility, it appeared to function as two businesses under one roof: a custom shop producing hand-built dream cars and a highly organized chassis manufacturing operation.
Josh described the company's design philosophy as broad rather than style-specific. Instead of focusing only on traditional roadsters or hot rods, they pursue whatever platform seems technically interesting or culturally relevant. That includes vintage and modern builds, two-wheel-drive and four-wheel-drive vehicles, stock-height and slammed applications, and suspension layouts ranging from bags to coilovers. When he first saw the Banks truck concept, his reaction was that it was crazy, but also compelling. A large diesel engine, air ride, aggressive stance, big wheels and tires, and Banks-specific hardware such as iDash instrumentation, transmission work, blower packaging, and even custom wheel-lug considerations made it a difficult but appealing engineering challenge.
Shop foreman John walked the team through the final assembly department, where projects receive wiring, trim, machine work, and final mechanical integration before heading to interior and completion. He emphasized that Roadster Shop's process begins long before a vehicle reaches the shop floor. Engineering, R&D, and CAD development happen in advance so the fabrication team already knows the dimensional targets and packaging constraints before cutting metal.
Because nearly every vehicle leaving the facility sits on a Roadster Shop chassis, the engineering team can model wheel tubs, transmission fitment, floor modifications, firewall changes, and engine-bay packaging in SolidWorks before fabrication begins. That preplanning allows the shop to spend more time on the custom sheet metal and visual details that make each build unique, rather than solving basic fitment problems reactively. In that sense, the company operates much like an engineering firm that also happens to build finished vehicles.
The tour highlighted how far Roadster Shop has moved beyond the narrow expectations implied by its name. One example was a Dodge D100 Power Wagon on the company's newer RS4 chassis, fitted with a Hellcat engine in an extremely tight engine bay. John noted that the RS4 platform represents a newer direction for the fabrication side of the business, especially with live-axle front suspension and three-link arrangements that differ from the company's more familiar independent-performance chassis work.
Another major example was a Jeep build that showed the company's growing interest in trucks, off-road platforms, and four-wheel-drive applications. John said this shift reflects Roadster Shop's habit of looking for what comes next rather than staying fixed in one category. He connected that evolution to projects such as the Colorado-based off-road build, which demonstrated that the same engineering intensity used in pro-touring cars could be applied to functional truck platforms. He also noted that the Jeep program had received substantial engineering attention, including direct work with Fox to tune the suspension so performance would match appearance. In his view, this is part of the next evolution of hot rodding: younger builders increasingly want trucks and utility-based platforms developed with the same seriousness once reserved for classic coupes and muscle cars.
Several in-progress vehicles illustrated the level of fabrication Roadster Shop performs once a chassis concept is established. A 1969 Dodge Dart on a perimeter chassis had its body welded directly to the chassis and sat extremely low, requiring extensive sheet metal work to package the vehicle's structure while preserving drivability. The build had also been shortened by approximately 5.5 to 6 inches for aesthetic reasons, a decision made in collaboration with the designer after evaluating the proportions visually. The car featured a hand-built spoiler, handmade bumper ends, and in-house-designed door handles that conceal an electronic actuator button for the door latches.
The Dart also demonstrated how digital scanning and repeated fit checks are used when packaging becomes extremely tight. Because the customer did not want a hood scoop, the intake would likely need to be machined, partially or entirely, to fit under the hood. John confirmed that this kind of work often involves scanning assemblies with the hood open and closed to understand exact clearances.
Another truck project showed how Roadster Shop modifies or hand-builds front-end sheet metal while trying to preserve an original visual language. John explained that the goal is often to make a vehicle look factory-correct at first glance, while someone familiar with the platform would recognize that the proportions and surfaces have been subtly improved. Material selection depends on the application: 19-gauge steel is common for large, shaped panels because it is malleable and gains strength from its curves, while 16-gauge is preferred for more structural mounting areas. Some builders use 14-gauge in certain places, but Roadster Shop chooses thickness according to the specific load and shape requirements.
The body and paint department handles everything from localized refinishing to full show-quality paint and body work. John described it as a compact but highly skilled operation, with only three people responsible for the final visual standards. Their job is to catch flaws that may not be obvious during fabrication and ensure the surfaces are straight and consistent before paint.
The adjacent metal-shaping area serves as the core of the fabrication shop. There, the team uses shrinking, stretching, cutting, chopping, hammer-and-dolly work, planishing, Pullmax operations, and whatever other methods are necessary to create panels that can resemble stamped factory pieces even when they are entirely handmade. A Cadillac project in particular was described as nearly jewelry-like in its execution.
John also pointed out one of the subtle but difficult fitment problems that separates high-end fabrication from ordinary assembly work: the relationship between a fender and a door where the geometry forces one panel to sit higher so the other can pass beneath it. Factory vehicles often tolerated mediocre gaps and alignment in these areas, but a custom build intended for show-level scrutiny cannot. Solving such a problem requires balancing appearance, panel movement, and paint protection in a very small area, even though casual viewers at a car show may never realize how much labor went into that 12-inch section.
After the shop tour, the Banks team met Mike, Roadster Shop's lead engineer for chassis and suspension. The discussion turned to the C20 project and the renderings previously sent over. Mike described the concept as different from what Roadster Shop normally sees, but said it had good bones and was worth pursuing.
The proposed direction was a slammed, bagged, long-wheelbase spec-series chassis adapted to fit the unusually large drivetrain package. That package includes a Duramax diesel, an Allison transmission, and a 3.8-liter supercharger. Although Gale noted that the 3.8-liter unit is smaller than some 5.0-liter blowers, he emphasized that it is more powerful while also being somewhat more compact. Even so, the team expected the induction system might still protrude through the hood depending on final packaging.
Mike said the first requirement was to get the truck to Roadster Shop for a full in-house 3D scan. Because the drivetrain is much larger and different from the company's usual combinations, they need to scan the exterior, frame, and underside to understand the global packaging problem before committing to geometry, frame dimensions, and mounting strategy. This would be Roadster Shop's first chassis specifically designed around a Duramax and its first around an Allison transmission, making the project a genuine departure from their normal pro-touring C10 work.
Mike outlined several structural changes the chassis would likely need because the truck is a long bed and will transmit substantial torque. Compared with a more typical application, the center section would likely use thicker-wall tubing, probably with a taller box profile. The frame would also receive considerably more lateral gusseting at the various joined sections, especially around torque-box areas and other mid-jointed or side-jointed transitions. The goal is to add as much rigidity as possible so the chassis can resist drivetrain loads without excessive twist.
Motor mounting would also be reconsidered. The factory GM mounts supplied by Banks are physically large and designed to isolate vibration for comfort, but that level of compliance may not suit this build. Mike suggested the chassis would likely use substantially less damping in the motor mounts while retaining enough compliance to keep the truck usable. The objective is to keep the engine planted in the center of the chassis rather than allowing unnecessary movement.
Front suspension geometry presents another challenge because of the Duramax's width, the desired 22-inch wheels, and the need to preserve steering function, exhaust routing, and tire placement within the fenders. Roadster Shop already has two front-module versions with different track widths, but Mike said they would need the scan data before deciding how much of the existing geometry could be retained. He specifically referenced preserving key suspension targets such as roll center, instant center, and anti-dive geometry while adapting the package to the truck's dimensions. The truck cannot become a parking-lot-only vehicle with poor turning radius; it still needs to steer properly and allow the tires to tuck safely when fully aired out.
One of the biggest departures from Roadster Shop's normal work is the insistence on eight-lug hardware. The truck will run 22-inch wheels with an eight-lug pattern, something the team acknowledged is uncommon in the hot-rod world even if it is normal in heavy-duty diesel applications. Mike noted that custom spindles and a custom rear axle would likely be required.
For the rear, the discussion turned toward using a Strange Engineering 9-inch rear end built around Roadster Shop's geometry and bracketry, but adapted for eight-lug axles. Exhaust packaging was also addressed. Banks wants dual 5-inch exhaust, ideally exiting on both sides. Mike said the frame rails would need a side path that allows the exhaust to move from the engine outward past the chassis and terminate where desired, all while maintaining the truck's very low ride height.
The meeting concluded with a practical plan: ship the truck to Roadster Shop as soon as possible, perform the full 3D scan in-house, and begin the engineering work from accurate vehicle data rather than assumptions. From there, the next stop would be Strange Engineering to see whether they could be persuaded to build the required eight-lug rear axle. That would determine whether the custom chassis concept for Lockjaw could move from ambitious rendering to manufacturable hardware.