best way to determine a rear end gear ratio

[chevyart]

what is the formula for determining a rear end ratio. my buddies vega has 26 inch tires,4 speed muncie, and a 355 sbc. he says the cam is a circle track cam and makes power from 3500-about 8000 rpms, say he wanteed to be coming through the traps at about 7800 rpms, what would be the aprox ratio to obtain the desired rpm do i have enough specs to complete the formula thanks chevy art

[zipper06]

You can use this formula EX: if the engine has enough HP to run 120 mph in the qtr.
The gear ratio would be a 5.00 gear. But i'm thinking 4.88's or 4.86 gear would work best. Ofcourse if the HP is higher you'll need to go down on the gear.

Zip.

http://www.wallaceracing.com/calcrgr.php

[MEMRACING62]

try this http://richmondgear.com/01calculators.html