I have a 67 GT Fastback that originally had factory air. I have the compressor and everything I need, it's just not currently in. I have to replace my alternator and it has a one pulley alternator in now. Is this correct or should it be a 2-pulley since I do have factory air?

 

it is corect my 68 has factory air and one pulley on the alt. unless your are tring to keep it original get a one wire chevy alt (its a universal that most people use to upgrade their tractors from 6 volt to 12 volt). its bolts up the same all you have to do is drill out the alt bolt hole because it is slitly smaller then the ford and you dont have to deal with all voltage regulator wiring.