I had similar issues in my '97 K1500 and after traveling the path you went down it turned out to be a loose connector/fitting on the back of the compressor. I cannot find the thread to where i posted it on here last spring, but like i said, it was the little black connector/sensor on the back of the compressor. I just wiggled it and the AC started working again.
I'll update if i can find the thread.
UPDATE =-)
Heres the thread with my AC problem...
http://67-72chevytrucks.com/vboard/s...d.php?t=395595