Most people these days tend to go too high on the rear axle gear ratio. If you're planning to run a small block V8, I'd recommend somewhere in the 3.50 to 3.90 gear Ratio with a 1:1 top gear in the transmission or a 3.90 or 4.10 rear end if you use an OD trans. Total height of the tires will have a pretty noticeable influence on cruise RPM. The most common standard shift rear axle in those years was a 3.70, and most of the automatics ran a 3.36. I believe aftermarket gears are available in 3.55 and 3.73, and drag race gears down to 4.56 or so.
Jerry
