Joe:
Here is a link to a gear ratio calculator that does a good job of letting you see what theoretical values are produced with various transmission/rear end ratios.
http://www.xse.com/leres/ss/calculator.html
My ERA is being ordered with the TKOII and 3.31 gears in the rear and 17" wheels. I felt that combination would give me the most "streetable" combination. Just plug in the values and let the calculator do it's thing.
DonC