1967 Pontiac GTO Frame - All The Rage

To accommodate the engine setback and the Bowler-built GM 4L85E overdrive trans, a new transmission crossmember had to be fabricated from 1.25x0.120-inch-wall chrome-moly tubing.

The driveshaft loop crossmembers were carefully placed so they could serve double-duty as seat mounts.

Due to the non-stock engine location, custom mounts were welded to the frame using 11/4-inch chrome-moly tubes to replce the Schwartz motor mounts. Final engine location was determined by the need to fit the throttle body/intake into the bulge in the stock hood. Test fitting all of the related parts is necessary to confirm adequate clearances.

The driveshaft loop crossmembers were carefully placed so they could serve double-duty as seat mounts.

Additional crossmembers/body mounts (again, 1x2-inch mild steel tubes) were added to replace the trunk body mounts and to provide support for the fuel tank and batteries. An existing crossmember was also moved a few inches to accommodate full-size wheeltubs (shown mocked up here). The rear framerails are narrower than stock, so a custom fuel tank is required. Note how the battery mounts are actually a part of the frame.

The very front of the framerails needed to be moved outboard by cutting and welding them to the outside of the remaining rails to make room for a Be Cool radiator. The nose of the frame was left a little long to be sure that there is also room for the intercooler, an A/C condenser, and an oil cooler. Shown here is the original frame piece sitting on top of the modified frame to better illustrate the mods.

You can see here that the upper coilover mount has been removed. It will be remounted in the exact same location, except to the front rollcage downtube. This is designed to give some more room to fabricate the turbo headers for the big Pontiac, while preserving the suspension geometry. The frame mounts for the upper control arms were not altered, so proper geometry is maintained there as well. An additional tube will be welded in from the front rollcage downtube back to the frame, thereby closing the loop for the coilover mounting point.

The front downtube of the rollcage is flanged at the firewall, so, again, the body can be easily removed from the frame.

The rollcage mounts were fabricated so that the 'cage bolts to the frame. That way if the body ever needs to come off, the 'cage can come with it.

Fabricating the floor is really a fairly straightforward process as it's broken up into some logical sections. The front two sections are the most difficult, since they have to accommodate the trans tunnel. Shown are the measurements for a driver-side floorpan. A good idea is to transfer the measurements to a piece of heavy card stock, so each piece can be mocked up and test fit before attempting to form it from sheetmetal.

This work is a lot easier with access to a sheetmetal shear and a metal brake. Once sure that the measurements were correct, they were simply applied to 20-guage steel to form the panel.

The second set of panels are a bit easier, as they are mostly square. These fit under the front seats. Notice the small raised lip on the inboard side of the panels. This is where the sides of the driveshaft tunnel will attach. At first, the panels are temporarily held in place by removable Cleco pins. Later, when proper fit is confirmed, No. 8 hex head sheetmetal screws are used.