There are several online calculators that will tell you what you need to know. Enter tire height, rear gear ratio, trans ratio and engine rpm and you will get an idea. The HP of the engine also comes into play as that will dictate how fast the engine will rpm and affect gearing. It helps a LOT if you have rear wheel HP numbers and/or current 1/4 mile times and data from finish line rpm. Otherwise it is a guess and you may end up with what you want or be off a bit. Google is your friend for finding various online calculators.