there's a whole section that covers OBS LS swaps.
but the stock 5 speed will be fine. the LS PCM can be tuned with or without transmission shift tables. if you're trying to race it, the 4500 is a bad option - yeah it's stronger, but the gearing sucks for racing & the clutch for either ain't that good for shifting fast or high in the RPMs. if you're 2wd, look into a T56 swap from a GTO (preferably) or a Camaro/TransAm