A few companies I've used,(1)LMC 1-800-222-5664 in Lenexa, KS, they have a very useful catalog with lots of 3D diagrams showing the parts and how they fit together.(2)Chevy Duty also in Kansas 1-816-741-8029, they're catalog also has diagrams.(3)Brothers is another good one 1-800-977-2767(4)Goodmark, <a href="http://www.goodmarkindustries.com," target="_blank">www.goodmarkindustries.com,</a> I also like to use because most everything they carry is GM Restoration Parts, but it's kinda limited what you can get from them ( as far as mechanical parts go). I've got a 69 C/10 that has what looks to me like a dealer install system on it, has this funny lookin' "Fridgedare" compressor mounted on this pedastool type bracket. I had a 68 C/10 that I let a local automotive a/c shop install a complete system on (I had a parts truck that they robbed parts off of) and they did a real good job. I had already bought the center and side vents for it and they installed all of it, new compressor, lines, duct work, they fabricated a really nice bracket for the compressor, cost me about 900 dollars and it worked perfect.