Jeri, the rear end gear you use will also depend on the transmission you use. A 4 speed trans will run at a ratio of 1 to 1, from the input to the output in 4th gear. 5 speed and 6 speed transmissions will have 1 or 2 gears that run at less than 1 to 1 (overdrive).

When you combine the gear ratios for the rear end and transmission, you want to try to have a happy harmony. If you run a 3.00 final drive (rear gear) and a double overdrive 6 speed trans, odds are the engine may be turning a idle (or less), even on a 65 MPH highway. At the same time, running a 4.56 final drive with a non-overdrive transmission, you could be spinning your engine at over 5000 RPM at 55 MPH.

Just a rough guess, but if you go with a 5 speed or 6 speed transmission, I'd look at a 3.42, 3.55 or 3.73 final drive. If you plan on a 4 speed, I'd go between a 3.00 to a 3.25 rear gear.