I did it several years ago on a couple Loadstar 1600 truck. The evaporators I got off EBay something like use on hot rod cars. Compressor mounts were from Scouts. The condensers I just went to the local wrecking yard and pulled a couple that were the right size for the radiator. York compressors and they came from the wrecking yard too. 

Sure I had to fab up brackets to mount the evaporators and condensers but not a big deal. New hoses custom made to fit. Systems have been trouble free and have been going for at least 24 years now. Biggest cost was the evaporators. I might of had $300.00 total into the systems and doubt it was that much. 

Or you couple mount a unit on top of the cab. I still have a couple those kicking around they contained everything in the unit all you would need to do is run hoses to the compressor.