All,
I was trying to order belts for my 91 GW and the belts I ordered didn't match what was on place. I had two Gates 7508 belts on the AC,Crank and Alternator. That was right. Then there was a single Gates 7580 running the PS pump, air pump, fan and crank. I finally figured out that the PO had flipped the pulley on the air pump so it was in line with the front groove on PS pump. I know how to put it back to the way it was designed but I'm curious if the belt change is a better configuration. Putting it back would add a belt and I've heard more belts are a drag on performance. No expert on the subject.