So I'm replacing my serpentine belt as the other day I saw a crack along the length of it and it may be on its last legs....but still good enough to last the drive to my friend's garage 45 minutes away. So I'm shopping for a belt at autozone and I see multiple lengths and rib sizes for my vehicle. Now I'm confused...

To help me start, what is the factory rib amount and length for the serpentine belt? Autozone is showing 25 inches all the way to 120 inches for the 5.0L GTA engine. I never thought it was this complicated :\

Would like some help as I would like to purchase the part tomorrow morning.

 

Run a piece of string around the pulleys where the belt runs to get a accurate dimension
or better still see if you can read an old part # off the belt you have
Should be 6 rib