AC/Serpentine question

[BrentBTK]

I have a '71 GMC with factory air...sort of... It was originally equipped, but the system is disconnected and I have the new compressor to install when I get to it. There is currently no compressor mounted on the motor. I am purchasing a new crate motor, and am considering one with a full serpentine setup already installed with new AC, PS, and ALT. So, my question is, will either the new compressor work with the old system, or will the "old" compressor work with the new serpentine? AC stuff is a mystery to me and I just don't know what is backwards compatible and what isn't. If anyone has had any experience with this, I'd love to hear. Thanks!