not calling b.s., but that seems like a lot, you mean 2 tenths like 10.61 to a 10.41? if so my powersteering days are numbered

 

back then the car was running around 11.70's

 

What you want to do is buy a 70mm 6 rib pulley, same as the tensioner pulley I got mine from autozone part number 231015 and put it where the alternator pulley is, you space it with a 1/8th" washer behind the pulley.

Use a 6 rib belt, the napa belt last numbers ending in 547, which is 54 1/4" and then you grind a little bit of the two alternator mounting bolts and it works awesome and won't toss belts.