OMG that's very rarely seen, Pat. That's the plenum of the 4dr Skylark cowl induction kit. Somebody's got to be looking for that part.
I actually had a 71 Skylark post car that originally had a straight six motor that had a plate made to cover the A/C hole in the firewall. I believe it was original. Even all the interior controls under the dash were non A/C..I used to have pictures but were lost in a divorce..
