If you’re interested, my parts guy matched my old one up with I believe a mount from 1970 thru 1972 Chevelle. It was the same height and bolted directly to the trans. The part was only $7.40 back in 1998. Also, if I remember correctly, I had to slightly enlarge the bolt holes in the crossmember and get larger diameter mounting bolts. Center to center was thew same. My receipt only has part #2378 but I don’t have the manufacturer.
If you want it exact, per Jim, re-vulcanizing is the way to go unless you can find an N.O.S. part.
Is it possible that your ’63 had factory air conditioning but all the components were removed by the previous owner? I thought you said the ’63 had automatic transmission that was converted to 4-speed manual. Could they possibly have made other modifications you aren’t aware of? All of the A/C components were removed from my car several years ago and you can’t tell that it ever had it except for a couple of extra holes for the A/C lines and some screw holes where the refrigerant lines ran on the inner fenders. The interior controls, ductwork and outlets were hung under the dashboard something like the old aftermarket units did.
I wonder what the 2M code in the ACC line of my ’63 Cutlass tag and Eric’s ’63 Jetfire tag means? It doesn’t correspond to any of the codes I’ve seen. I have several options on my car but the major ones are automatic transmission, air conditioning, power brakes and power steering. The holes in the fire wall for the air conditioning lines look like an afterthought but I have no way of knowing if they were made at the Fisher Body Plant, at the Oldsmobile Assembly Plant or at the dealership. I wonder what Eric’s car and mine have in common for the 2M code?