Plot thickens. I know that the 99VX sitting in the yards in Charleston does not have the same compressor as my 01. I assumed it was a difference associated with auto climate control.

The GM compressor physically fit in the truck, but the fittings were not even close to the same. One might be able to swap all the lines and make the GM model work, which can be had for 100 bucks or less on Ebay. That might be worth the effort. I tinkered with all this at the beginning of my relationship with my VX. I wasn't as comfortable tearing into that stuff back then. If I was not in the Arabian Gulf right now, I would probably take it apart and hack out the old lines and do the swap....then I could sell my two spares and perhaps pick up a new welder with the cash