us7race is dead on, if you are turning about 6200 in the 1/8 mi. lites, useing this calculator, and you want to turn 7,000 rpm. It comes out to 4.63 gears. BUT, there could be a hooking problem with the b/blk. We run 5.29 gears with a s/blk and run 5.90@118 and 10.5W tires but it doesn't have the torque of a b/blk.Here is the caculator that will help you decide.
http://www.wallaceracing.com/gearcalc.php
Zip.