Right now I’m installing a factory A/C system into my dump truck I pulled a working unit out of a truck with a motor that liked to fill the crankcase up with antifreeze as fast as you could pour it in . The trucks have all the mounting provisions to add A/C . As for an aftermarket unit there’s not a lot of room to put stuff . Most of the compressors on the universal kits is at least twice as big as the factory unit . Finding a parts truck with the setup already in it would be the simplest and probably down the road cheapest when all done
Mine has AC which was added by the dealer when they rebuilt in in Cebu, Phillipines. It looks like a miniturized Sanden compressor. Don't believe I have ever seen a compressor so little. May or may not be available in the US. Fred