[jeffschevelle]

I can't speak from experience with the AC differences in a 68-72 A-body shell. But I know from experience that on both 61-64 Impalas and on 64-67 A-bodies, (A) the firewall / toe-board section is different, (B) the part of the firewall above the seam is different, (C) the right inside kick panel / cowl section is different, and has the big "vent" hole farther up and a completely different shape, and (D) the part of the right kick panel / cowl section outside the car (behind the fender), is a completely different shape (not just the holes, but also a larger stamping that goes farther straight down towards the ground before it bends back towards the rocker)

Actually, (C) and (D) are a single piece of sheetmetal, but part is inside the car and part is outside, and you cannot change the entire piece in a single unit at one time without cutting the entire right side of the cowl off the car.

So you can easily slice new holes in the firewall for AC; but to alter the right side of the cowl for AC you have to add metal at the lower part of the interior vent hole, reshape the upper part of the hole, and "build" an additional box area at the lower part of the outside of the right corner of the cowl. Can it be done? Yes, as I have done it to a 63 Impala and a 67 Chevelle. Is it any fun? Heck no. Can it be done without taking the front fender off? I seriously doubt it, and sure wouldn't want to try!

Again, no idea about 68-72, but I would think the complexity of the AC cowl differences was at least as involved as on a 67.