I recently installed a j&S 240 amp high output alternator. I'm having one hell of a time trying to find the right serpentine belt. The website says to get a serpentine belt that is a half an inch shorter. I've tried this route going through NAPA Auto parts and I have been unsuccessful. I went and installed a brand new OEM belt hoping that it would work, but it's not. It squeaks and squawks and there's voltage drop. If anybody has links or the exact belt that I need for an aftermarket high output alternator I would greatly appreciate it.

I assume you have a QR25, RockAuto says a Dayco 5060564 is OE. The next size down (0.4" shorter) is a 5060560. You can of course xref the Dayco number to just about anything else. Here's the chart:

https://www.daycoproducts.com/stuff/con ... 060515.pdf