I bought a Red Dot R-9777 cab roof unit. Artisan is correct, in that this does contain the evaporator, condenser, pressure switches, charge ports, fans and controls for both, and the receiver. All that is needed is a compressor (24v clutch or resistor or 24/12 relay) and lines to it. I bought mine NOS from eBay, as this was the only unit I wanted, cool air is instantly effective if dropped from the top down since it falls rather than having to fill the cab with cold air until you are surrounded by it. Warm air rises, etc.... Also all the H1 kits take up a lot of cab space which there is none of already. I wanted A/C only, and the R-9777 can be optioned with or without a heater core inside of it. Mine was without, which I was fine with. A few have put an MRAP HVAC box where their stock heater core is, and this looks OK, but will only have limited cooling ability as it can't recirculate the cool cabin air. I have an 8.3 925A2, and made my own compressor mount. Bought the correct kit then resold it because I want to stay serpentine belt with spring tensioner. The links above for mounts are ungodly expensive. I would suggest looking at truck parts yards, a lot of 855's had A/C, you should be able to grab mounts to work for you for under $100. You can even get an alternator pulley with additional groves and drive it above there, for example. Here is a few shots of my R-9777, not yet installed:
http://www.steelsoldiers.com/showthread.php?137049-Red-Dot-R-9777-Install-on-M939A2 I did not use the Sanden Flex-7, there is a higher output compressor from them that I went with on their website, forgot the name of it. 12V clutch only on it, so I will just use a 24 relay and feed the contact side 12V, and 24v on the relay coil side from the rooftop unit switch.
