Will I need the wiring harness from a doner with AC and is the AC wiring harness seperate from the main wiring harness?

 

This is going to be a big job. Sounds like you haven't started yet, but are still in the planning stages. Have you looked at any of the aftermarket vendors to see if they offer an aftermarket system for your truck? It would be self-contained, designed to use the newer refrigerent, and have the newer more modern compressor and other components.

 

you are adventurous yes you should get all the cotrols from a donor tuck the wire harness the vacum harness heater control
and cable duct work dash panel vents hoses .... ever thought about just finding an AC cab it would be easier just to change cabs