Our ring-and-pinion kits are from Reider Racing and National Drivetrain. National Drivetrain also sells this shim kit from Motive Gear that has everything you need (including excellent instructions) to do a proper third-member install. To go with our 1.96 transmission, we chose a 3.08 ring and pinion. That combination gives us a 6.04 final drive (1.96 x 3.08 = 6.036), which should be just about right for our half-mile home track. We also have a 3.27 manufactured by Precision Gear, which will provide a 6.41 final drive, for adjusting.