Newbie here starting my 1st A body and need a/c help

Mikey, I don't remember part #'s sorry. Check with Classic Auto Air or Bouchilon about the brackets. The "shorty' compressor is #7312 as stated above. You probably won't need this compressor unless you're going 6 bbl. The normal Sanden compressor you see all over eBay should work. Watch for 12v versus 24v clutch when purchasing.
I stayed all Chrysler a/c except the compressor. You'll have to make up new rubber lines anyhow and the a/c shop can make them fit on both ends. Old to new.
I have a '74 Duster and all the new a/c evaporator and heater core were available. I rebuilt heater/ac box before reinstalling it.
I installed a hi/lo switch at the drier rather than the original lo pressure switch. Looks the same just makes a/c safer with the pressures. It was available from Classic Air. Should be available at any a/c shop. And surely go to 134 Freon.
Good luck.