Off the top of my head, there's the option for 3.08, 3.42, and 3.73

Most 4 doors got 3.42 or 3.73's.

If you have the 3.08's, do NOT go to a bigger tire, lol.

 

GU4= 3.08 Ratio
GU6= 3.42 Ratio
GT4= 3.73 Ratio
GT5= 4.10 Ratio
G80 = Limited Slip


look for any of those on the RPO sticker. theres a handy calculator on s10forum that will explain all the codes. its a good idea to have a pic so you dont need to check your truck if you or someone else has a question

 

I got the 3.42

GU6

 

I really need to dig out the RPO code for the 8.5" axle... I'm pretty sure there's one...

 

have fun...

http://aplsweb.com/Topics/TopicPix/RPO.pdf