A/C Qeustion on a '72

I have a '72 Camaro that somewhere down the line had it's factory A/C unit ripped out and replaced by a heater box and sheet metal patch:death: . Am I better of replacing it with a later (mid '70's to 81) unit that I already have or should I find an original unit? If original, what years and models interchange? Would a unit for a '73 Nova fit? Also How can I I.D. what year the A/C (HVAC) unit is? Can a short style compressor be used with the older a/c unit?

Thanks:usa:

btw: The car was originally Maroon with magnesium slots, plywood (literally) int. trim and had the entire nose and rear spoiler molded together to the body with extensions welded to the fenders over the headlights. Maybe someone out there knows this car.

:cry: anyone :cry: ?