I had the same problem one time with an aftermarket pump I installed - a Hepu I beleve, but that's beside the point. The pump casting was so crappy that the upper belt cover wouldn't sit all the way back into the groove the way it should. Unfortunately I didn't realize the problem until the pump was all bolted up. Had I known it was going to happen I would have filed out the pump casting a bit before installing it. I ended up putting one thin washer on each of the four studs BETWEEN the pulley and pump flange which brought the pulley forward enough the clear the cover, yet it wasn't so much as to cause any significant pulley misalignment.