they're good for ~320hp. It is a pretty good transmission for a stock mustang but if you're pushing a decent amount of power, look into a T-56 if you're going the 6 speed route, or a TKO-600 if you reallly want to pound the crap out of the tranny without worrying. Personally I like my T-45, it shifts very smoothly, and takes all I can throw at it