Gear Ratio Selection

there some calculators for that type of stuff around the web...i know bigblockdart.com has one....i punched some numbers into a calculator with the info you gave and it says youd be doing 66 mph at 3000rpm...thats with 0% converter slippage....all converters slip a bit, so with a number entered in for that you may get a different number...heres the link to the calculator i used

http://www.speedwaybids.com/calcs/mphrpm.html