I need a near-complete harness assembly for my 82 K20, and the name that keeps popping up on the web is Painless Wiring. The problem I have wive them is that they're pricey. A complete wiring harness for my truck runs about $350.00. Personally, I think that's a bit much. Autozone carries Painless wiring products. You might find what you're looking there.
As a suggestion for both of you, id try looking in a junkyard, or calling them at least, i know it takes a lot of time to sift through a yard, but i bet there are plenty of k20's in there and a few 96 gm trucks, if nothing else cover your bases there. my $.02