I want to install lower gears in my 89 IrocZ. I was considering 3.45 or 3.70(It currently has 2.77 and is a 9bolt), and possibly a higher stall? The motor is basically stock other than Air foil, ported plenum, SLP intake runners, ported intake, headers, high flow cat, and 3 inch exhaust, AFPR, power pulleys, and a an ATI Procharger(with 9 pound pulley). Was considering a Vigilante convertor they seem pricey but I hear they are well worth it. Any suggestions on gears and stall from you guys would be greatly appreciated. I want to keep it streetable but maybe run mid 12's in the quarter. Does this sound possible or reasonable. Thanks again.

To the best of my knowledge, there are not many choices for the 9 bolt rear ends. TPI engines that make peak torque at around 4800 RPM, would not benefit from alot of stall or gear. 3.73s might be a bit steep, but they might be the only gears avaliable for your rear. For stall, I would not exceed 200 more than the stock converter. Im sure Vigalante can help the best with the applications. A Procharger with your mods should put you in the low 13s to high 12s, with good traction.

Thanks for the advice. I will try to gear it around 3.50. I didn't want to go to low since I'm not making alot of top end horsepower,but wanted low enough to help me off the line. Thanks again.