In our January issue, we showed you the installation of a six-point cage, torque boxes, and subframe connectors in the Brazen Charger. Making a street thrasher worthy of 10-second times on a sanctioned NHRA course takes lots of modifications and compromises. we needed to ditch a lot of weight to lighten up our hefty B-Body if we ever wanted to see sub-11 times; the first to go was the dilapidated air-conditioning system.
Our Brazen Charger came from the factory with air conditioning. After the A/C was junked for the sake of weight loss, the gaping hole in the firewall was too much of an eyesore to be left. | 
First, a piece of cardboard was cut to match the outer diameter of our template. We wanted to enclose all the A/C outlets and other predrilled holes from the factory. The Sparco box and wire loom were unscrewed and pulled off to the side for temporary clearance. Take the cardboard template and trace out the pattern for your cutting wheel. Follow the outline carefully, so not to mar the firewall. The result will offer a section of firewall that will help to shape the patch panel. | 
Trace the pulled portion of the firewall on a piece of 16-gauge sheetmetal. Try to cut the patch as close as possible with the sheetmetal sheer. Using the grinding wheel carefully finish-fit the patch panel to the hole made. This is the most time consuming part of the project--the tighter the fit, the cleaner the replacement can be. some minor body filler will be used when the engine compartment is painted, so the smaller the weld made to fill in gaps the less filler will be needed to cover up the surgery. |
Without showing the play-by-play on how to properly remove the underdash unit, we will show you how an easy template can be made and a near-perfect patch panel can be fabricated to fit within an hour or two. We went to Cameron Shaw's shop in Southern California to see how a nice afternoon project can be done correctly.
The tools required will be a grinder with a cutting wheel, a grinding wheel, a flap disc or polishing wheel, a sheetmetal sheer, and a MIG welder.
Use the flap disc to clear away the paint a good 3/4-inch from the edges of the patch panel and firewall. That way a proper weld can be made. We used a magnet to hold the patch panel in place as small tack welds were made at all the major corners every each inch or so. Metal is prone to warp and shrink upon welding, so Cameron used a flat screwdriver to keep the patch in place. | 
The flap disc on the grinder was used to smooth the welds down so a minimal rise was visible from the patch panel to the existing firewall. Be extra careful not to overheat the metal or grind through the welds because this will cause you to have to start all over again. (We speak from experience.) | 
As a temporary fix, we primered the patch panel with some rattle-can paint. When the car is ready to be painted, a thin coat of body filler will be used just to ensure the final cosmetic look. The firewall will then be drilled to hang the wire loom, fuel lines, and ignition box. |