3.2 alt pulley with stock lower, Belt?

[Ceanes]

I currently have a 2.80 upper pulley and stock lower with a 90mm idler pulley. My question is Im going to be getting a PA 170amp alt to help out my stereo and I need to know how much bigger belt I would need using a 3.2" pulley? I have a 74 inch Gatorback belt right now and not sure how much longer a belt I would need and still be pretty tight. Any help would be great.

Thanks
Chuck

 

[apg2369]

Go To Napa And Get A Few Belts Like A 75' 75.5' And A 76

Just Go Out Side And Try Them On...tell Him You Wont Start The Car ....just Want To Try Them On.

If He's Cool He'll Let You Do That. Just Bring A Breaker Bar With You.