I am running a 3.08 posi in mine. To compensate for the gear size I am running a 3,500 stall. With running some 26 inch Hoosier Quick Time Pro's I have made a 13.4 @ 97 with my first time out this year with my new set up. Found out that my factory fuel pump could not hold up to my new 400, so I had to pull back out of the gas at about the 1,000 foot mark. I'm installing a new fuel system this week and should have high 12 when I hit the track again in 3 weeks. So I would say you can get good speed out of a 3.08, just don't expect good 60 foot times.