There are some calculators out there but I can't remember where - I thought mustangworks...

Anyways - if you want to find out what gears - the best thing to do is cruise with another car at about 60 or 70mph and post the exact mph and rpm that you run at, tire size, etc. and the gears can be figured out through a caclulator. You need the other car b/c your speedo is off. I remember reading a post about this on the corral somwhere -will see if I can find it.