Ok, over the course of the last month, I have replaced the idler pulley, the tensioner pulley, the alternator (needed), and last week the belt. I had the truck in the shop today to get the alt replaced under warranty. the mechanic wanted to replace the belt, because he said it was jumping around. The belt I bought is a Dayco belt. From what I can tell by its tracking pattern, it has a 1/8 inch band at the front that is wearing more than the rest of the belt topside.
the only thing I can tell that could be the culprit is the tensioner itself. It seems to be at an angle with the pulley angle towards the front of the truck a bit. Also, the belt wants to run near the face of the pulley. Is it possible that the tensioner needs replacing?