KB Belt length and idler pulley size

[08StangGT_CS]

So yesterday while driving my car the idler pulley on the right of the alternator failed which in turn shredded my belt. I know I've read this info in here before but couldn't find it trying with different search combinations.
1. What is the correct belt length? I am using the stock pulley which I believe is 4 in. Also, does anyone happen to have the Gates part number for it? Any of the chain auto parts store that will carry what I need?

2. What size idler pulley was the one I destroyed? It's on the right side of the alternator and labeled pulley 3 if you have the KB belt routing schematic.

Thanks,
HC

 

[TexasBlownV8]

Is it one of the smooth pulleys? I have an extra one. Autozone has both the smooth and ribbed idlers.
Not sure about the belt length. I'd like to know the length as well.

 

[zipperhead]

I think these belts are custom manufactured for KB. Get the pn from your install manual and call KB. Order two.. lol

BTW I know of at least two different sizes. Unfortunelty I have them both now

 

[08StangGT_CS]

I called KB and said the belt is 124.7" long. The pulley I destroyed is a 61 mm idler pulley. I should have asked if it was a smooth pulley. Oh well, I got BBR overnighting me both items now.