My dad ordered his 79 Wagon how he wanted it. He clicked and paid for the AC option but when the car came, it did not have AC. Dealer gave him two choices, either to order another car and wait for another 6-8 weeks or they could install the dealer air. He chose the dealer air and it was garbage from day 1. It went back to the dealer multiple times when the car was under warranty and then my dad threw in the towel after the warranty expired. It is still all in the car. So as far as interchangeabi lity, everything seems different than factory AC. AC box, hoses, engine brackets, belts etc.
Years ago, I had an 80 parts car that had factory AC that was 85% complete. Just missing the engine brackets. I saved all that for my dads wagon so I could make it as he ordered it but I let all that stuff go with my cruising wagon when I sold it as it was going to Arizona. Did you buy the car?