LokJaw’s engine bay isn’t getting dressed up with flat panels. It has to be built around the hard points of a supercharged Duramax swap: header clearance, front-feed intake routing, hood interference, core support shape, brake mounting, wiring bulkheads, and the size of the Allison and driveshaft tunnel. That’s why the sheetmetal plan starts with keep-out zones, real suspension and tire clearance, and airflow paths through the grille and lower valence. The goal is simple: make the firewall, tubs, tunnels, and airbox areas fit the hardware cleanly, keep service access where it matters, and avoid building pretty metal that crashes into the parts that actually make the truck run.
After a stretch of late nights and weekend work, the team completed the last round of prep on LockJaw and loaded it onto the trailer for delivery to Empire Fabrication. The truck had been pushed hard right up to departure, with final adjustments continuing into the day it left the shop. Once it arrived, the handoff focused immediately on what Empire needed in order to begin sheet-metal work efficiently.
The project is being built with support from AMSOIL, Roadster Shop, and Nitto, and the immediate goal of this visit was to transfer all the packaging decisions, mock-up geometry, and fabrication constraints that had been established so far. With the truck finally out of Banks' shop and into Empire's, the discussion moved front to back through the vehicle so the next phase could begin without guesswork.
At the front of the truck, the team explained that the headers had not yet been built, but were already being designed in CAD. To allow Empire to start the tubs and surrounding sheet metal, Banks had created physical keep-out zones showing where the headers would occupy space. Those mock-up pieces defined the maximum allowable intrusion so the tubs could be built without interfering with the future exhaust routing.
The hood hinges were also reviewed. The star-shaped pieces shown on the truck were intended as final pieces, but the hinge arrangement itself was still mock-up only and would be redesigned. In its current form, the hinge was in single shear and had too much wobble, and some of the parts were only plasma-cut placeholders. The spring arrangement was also still in development. The upper holes in the hinge area were intended as spring mounting points, while a lower hole would serve as a brace. The spring would sit lower in the structure so it would not interfere with the sheet metal that Empire planned to run through that area.
The intake system had progressed far enough that Banks could define the final path even though some pieces were still missing from the truck. A 14-gauge flange had been established using a matching cutting jig, with locating holes duplicated so the fabricated parts would register correctly. From that flange, the plan was to run a short section of 5-inch tubing toward the headlight opening, ending in a velocity-stack-style radiused entry. The filter would drop into a flange in that area and tuck upward into the available space.
Clearance to the front tires was extremely tight but acceptable, with only a small gap remaining at full steering lock. To make the intake path work, the truck had been converted from its earlier 1966 grille arrangement to a 1960 grille with dual headlights. The inner headlight would be removed, allowing the 5-inch intake tube to pass through that location. This change simplified the intake dramatically. Earlier, the supercharger orientation had forced a rear-entry concept that would have routed intake plumbing around the floor. By rotating the supercharger, the intake became a much simpler single-bend 5-inch tube dropping into the filter location.
The hood, however, would need to be cut. The supercharger itself did not extend past the flange line and still had roughly an inch of air gap, but the intake path and surrounding geometry required a notch in the hood structure. The doubler in the hood would be cut and then reworked to restore stiffness. Based on the CAD work, the interference was localized to a small area rather than requiring a large opening.
With the intake now entering from the front, the firewall could be much simpler. Banks indicated that Empire should be able to build a flat firewall across the truck. The brake bracket had already been mocked up on the firewall plane and bolted in place, with some adjustment still available under the dash if needed. In fact, almost nothing permanent had been welded to the truck at this stage. Most of the development work had been done with bolted parts so geometry could still be revised.
The core support had previously been too flexible, essentially floating on only the lower bolts, so braces had been added to stabilize it. Those braces cleared the tires at full droop and could be retained or revised depending on Empire's final sheet-metal approach. The upper cut geometry around the inner fenders and support structure was considered final, and Banks suggested that Empire echo some of those shapes in the surrounding panels. The supercharger and intake geometry also influenced the styling direction, and there was interest in carrying those forms into the finished metalwork.
The lower front valence needed one important aerodynamic revision. As built, it dipped under the core support. Banks wanted that area made flush with the bottom of the core support so incoming air would be forced through the cooling package rather than spilling underneath it. The truck would also carry an accessory cooler package mounted beneath the main cooling stack, including ducting for the cooler and the power steering cooler, so controlling airflow through the nose was a priority.
Several front-end details still needed to be resolved around the intake and cooling package. The air box would require trimming in the front structure where it passed toward the headlight opening. The existing hood latch also interfered with the condenser fins and would be removed. In its place, the team had brought Mercedes rear latches and was considering mounting them slightly inboard off the supports, pocketed into the surrounding structure for a cleaner installation.
The steering column opening and firewall relationship also needed refinement. The column position would likely be pulled back slightly with a longer shaft so the end of the column sat flush with the firewall rather than leaving it recessed in an empty pocket. The angle still needed adjustment under the dash, and the firewall shape around the column would need to account for the dash taper and seam locations.
Banks also asked that airflow through the grille and hood remain functional. Air still needed to pass through the radiator, so any sheet-metal treatment in those areas had to preserve that path. The turn-signal buckets had already been removed because the revised top shape of the core support would interfere with them. Replacement low-profile lighting was planned. Additional CAD-designed reinforcement pieces would later be added back into the cut core support so the final structure regained its strength, both at the top and bottom. Empire was asked not to finalize core-support sheet metal until those reinforcement pieces were provided.
The wiring strategy centered on mil-spec connectors and careful bulkhead placement. Banks had three military-style connectors available, believed to be 32-pin units, along with an A/C bulkhead. The main question was where to place them so the harnesses could be hidden while still respecting bend radius requirements. One motor-harness connector in particular needed about 3 inches of clearance behind the panel because of the heat-shrunk harness wrap and connector body.
A recessed rear wall behind the engine, set back about 3 inches, was proposed as the cleanest solution. That approach had already been used successfully on another SEMA build. For the A/C plumbing, the preferred solution was to hide the bulkhead and route the lines along the inside of the tub. Depending on packaging, either a four-way bulkhead or a straight inline arrangement could be used. The goal was to keep the plumbing concealed while still allowing two lines to continue rearward toward the pump, which was already mounted in its intended location.
Inside the cab and floor area, Empire could begin work on the firewall, transmission tunnel, and driveshaft tunnel even before the rest of the engine-bay sheet metal was finalized. The truck would need substantial tunnel work, especially because the seating plan was still unresolved. The team was considering a hybrid between a bench seat and buckets, but no final seat had been selected yet.
The driveshaft was expected to be a QA1 carbon-fiber unit measuring 3.25 inches in diameter. The packaging model used a 3.750-inch clearance envelope on that 3.25-inch shaft in a 3200-series driveline arrangement, leaving only a modest air gap. Because QA1 did not offer a slip shaft for this Allison application, the transmission would require a slip-yoke-style solution instead. Motor mounts were described as fairly stiff, so Empire was advised to allow roughly half an inch of clearance around the transmission and related components. The tunnel could then drop down tightly behind the transmission to minimize intrusion into the seating area.
The truck would use drive-by-wire, so pedal placement remained flexible. Under the dash, packaging still had to account for the Vintage Air unit, the ECM, and the TCM, all of which would influence final firewall and tunnel layout.
The exhaust system was planned as a set of four-into-one headers feeding pipes that would pass under the body mount and continue under the body along the outside of the frame. The concept included a V-band straight section so the truck could be configured either with a straight-through muffler or as a straight pipe. Because this Duramax combination is supercharged rather than turbocharged, it would not benefit from the muffling effect of a turbocharger. The team expected it to be dramatically louder than a conventional straight-piped turbo diesel. They referenced earlier testing of a supercharged engine before twin turbos were added, noting that with zoomies it shook the entire warehouse.
On the front accessory drive, the FEAD package was largely defined. Aside from idlers and tensioners, which were located inboard of Banks' custom pieces, the system carried the alternator, A/C compressor, and power steering pump in place. The power steering reservoir would likely be fabricated rather than using the factory plastic reservoir, which was considered visually unsuitable for the build.
The intake manifold also incorporated a charge-air cooler with rear-exit lines. Because those fittings would affect firewall recess depth, Banks committed to drawing the fittings in CAD early the following week and providing a printable template that could be positioned on the back of the manifold. That would let Empire build the rear wall and firewall recess accurately without waiting for every final hard part to be installed.
Empire and Banks also discussed what material to use for the remaining air-box and engine-bay sheet metal. Some of the mock-up pieces had been made quickly in 16 gauge steel during the rush to get the truck out the door, but there was immediate recognition that aluminum might be the better final choice. If made from aluminum, 3003 alloy could be shaped more easily, including the compound curves needed for the domed upper and lower sections, and then welded into the finished assembly.
At this stage, the air boxes were conceptually built but still likely to need hand-formed compound-curve pieces. Banks noted that many of the bends so far had simply been slip-rolled, and Empire's metal-shaping equipment would be useful in refining the final forms. The hood would come off first to make access easier, and with only four nuts holding it on, two people could remove it quickly.
The immediate schedule was aggressive. Empire estimated roughly two weeks, though the shop was already full and the workload was heavy. In addition to the engine-bay and floor work, there were also roof holes and a few body blemishes to address. The bed would come later, but for now the priority was to turn the extensive mock-up information into finished firewall, tunnel, intake, and front-structure sheet metal while preserving all the packaging decisions Banks had established.