Don,
Last year I installed a factory A/C system in a earlry 91 W-250 I had purchased with only 14K mi (original). I basically stole the truck for only $6500. 00 from an old dry nut who retired in Buckeye AZ.
I purchased a complete factory A/C system from a wrecked 90 D-250 Cummins for $550. 00 From Auto Paradise in Glendale, AZ. The system included a compressor and mount bracket, a complete heater box (with an A/C evaporator), an instrument bezel with the A/C vents, a Heat / A/C controller, a condensor radiator, a bunch of hoses ( mostly junk), and all of the necessary plastic ducting which installs under the dash. The entire installation took me a weekend to install, including cutting the vent cutouts in the dash (near the glovebox). The truck was allready wired for A/C, so the components plugged into the existing wire harness. I ended up replacing all of the high and low pressure hoses with aftermarket ( Factory Air) hoses from Autozone ($75. 00). I had a small leak in the condensor which needed to be repaired at a local radiator shop for $30. 00, and a very slow leak in the compressor shaft seal. I ended up replacing the compressor with a remanufactured one from Checker Auto Parts ( same as Schucks and Cragen) for $175. 00. To make a long story short, although it was a lot of work, I felt it was well worth the effort because the system worked great and looked like a factory installation, not an aftermarket abortion hanging under the dash.