I concur with Randomguy - 4.56 ratio at a MINIMUM. The 4.88 ratio is probably the better fit, though. There is a formula to help with the numbers. (Those in the know - chime in!) I changed out the gears in my c1500, 5.7 from 3.42 to 4.10 to compensate for 31" tires. Truck runs great! I used the...