Seems like they are different from bike to bike.
I tried a Dayco Top-Cog 15290 (29" long), and it was too long. The adjusting bolt was all the way up in the notch, and the belt was still too loose and squealed. :|
Then I tried a Dayco Top-Cog 15280 (28" long), and it was too short.
The adjusting bolt was all the way down in the notch, and the belt was way too tight - even after 50 miles of riding. :roll:
@Joe: Now I know what you were talking about when you said it was a pain in the ass to put the belt on...after 1 hour I ended up laying the belt on the pulley and pushing the starter...there was no other way....
I just ordered a #15285 (28,5" long), cause I don't wanna destroy the alternator bearings - the #15285 should fit perfect on my bike.
I think everyone has to try which one fits best for his (individual) bike.
I use the Dayco Topcog #15315 which was the one that came stock on my 2000 small block. It is a bitch to get on, at least for my unmechanical ass and have to do a lot of creative prying every time.