On to cutting more fiberglass. Remember, measure twice cut once. Upper heater case requires a cowl vent. We marked the centerline of the body. That was the easy part. The cowl vent had to be centered no matter what, it was the front to back position that had issues. Simply making a template from the outside of  the body had us uneasy. So we cut a hole about an inch smaller all the way around in the position taken from the steel body. Then a piece of cardboard was fastened to the upper case opening and a centerline was scribed which was easily determined by the existing screw holes. the case was positioned underneath and against the inside of the

firewall but was very awkward to find an accurate front to back position. So we bailed on that idea. We knew the case had to clear the inside of the firewall by factory specs. A straight edge was held against the inside of the steel body firewall up to the front of the cowl opening edge. A measurement was taken at the end of the straight edge then that measurement was duplicated to the fiberglass body. We now had an accurate front to back measurement. A template was made of the opening from the steel body with a centerline on it. Lined it up with the body centerline and the front edge. Tape was put around it for a saw line. As you can see the

rough opening is clearly 1/2" too far front. If we would have cut it to size the heater box would have interfered with the inside firewall by the same. A jig saw was used to do the surgery following the tape line and the original grille fit perfectly. It sits back the 1/2" further than stock, but that's the way it must be. The placement of the thicker glass firewall is what makes that determination. It now has the same firewall clearance, clears the brake pedal bracket and we just might be able to clear the right side kick panel with the lower part of the heater case, we'll find that out later.

Lets talk a little about fiberglass repair. This will come in handy when you don't follow the ever important rule of measuring twice and cutting once. Unfortunately I did the opposite. In laying out the drain hole for the heater box I measured from the side of the hole on the original firewall to the centerline of the body we had established and failed to add half the hole to the centerline. Needless to say the heater box interfered with the brake pedal bracket. Ok, cut twice  and used the piece I cut out to fiberglass back in. Pretty straight foward. I ground down both sides of the firewall then used some Gorilla tape to back up the plug, smeared a thin coat

of resin on, a piece of fiberglass cloth and another coat of resin to cover it all up. Waited for that to set up, removed the tape then did the opposite side. Left it set overnight then ground it smooth. One thing I want to caution you on is grinding. WEAR A MASK. This stuff is nasty. Next I will show you how we layed out the cowl vent. Fiberglass and steel bodies do not have the same dimensions when it comes to thickness. Compensations have to be considered. You just can't trace a pattern and have everything fit. But then again maybe if I would have traced the drain hole I wouldn't be doing this post.