i am putting in a 355 with near 400 hp currently have 273 gears even though its a new engine i am changing the cam to a comp 268 extreme energy.i have a 88 iroc with 29 inch in the rear and a 700r4 i want opions on 342s or 373s?im not going to beat on it i just want the rps to match the cam which is 1600-5800

 

Welcome to the boards. I might suggest checking out the other forum boards and posting in the proper one in order to get the best responses.

While I cant do the math in my head to figure out what RPM you'll be at w/ what width tires, your rear gear ratio, drive gear ratio, etc... I can tell you that the higher you go the easier your car gets winded, but at the same time, the faster it'll go down the track.

Is this for a street/strip car? Or just a daily driver? If a daily driver then a 3.43 gear ratio would probably suffice for you.

If you have a 9 or 10 bolt, you'll have a series 2 carrier, you'll need to upgrade to a 3 series carrier so that you can put the 3.x gears in there....

while you upgrade, you might as well buy a posi unit.