I ran into the long short deal too! This one has been batted around, and it's my best guess that it probally has to do with ac & w/o ac cars, and I think that the w/ac pulley aligns the belts.

I don't remember whether the problem was with the alternator belt, the p/s belt, or both, but I do remember that the ac pulley corrected the problem. The thing is that it looked cobbled together with the blank "v," so I changed to the short snout pump.