If you're working out mostly to benefit your bowling, I would focus upon legs, core, and flexibility; strength training (building muscles) doesn't really do a whole lot to help your bowling unless you are rehabbing from an injury.
As far as adding speed and revs goes, faster feet should equal faster ball speed. Adding revs has to do with the your arm swing and release, and it tends to be freer swing = more revs. As such, usually, the more you try to put on the ball the less you actually get on it. I mean, look at E.J. Tackett; he looks to be about 5-6, 135, yet he absolutely rips the cover off of the ball. If size and strength determined revs, he'd be lucky to kick 5-8-10's out. I'm 6'2, 230 and pretty solidly built, yet he makes me look like a pansy in terms of how much we both put on the ball.