I run a GT67 with a .81 housing. It is a bit large for a 5.3L but for drag racing and great top end it is the way to go. For better street manners the GT35 works excellent. Just gotta decide what you wann ado and how tolerant of lag you are.

The STS and ATI are both great performers but work totally different. The STS gives you a ton more power on the low end (depending on turbo sizing) than the ATI but is more unpredictable in that the power can come on so suddleny that you have to be careful where you punch it or else tire spin can get you out of control really quick The ATI is going to be much more linear and easier to predict. The turbo can use a much smaller torque converter which is great for towing or daily driving. The ATI will need a larger TC which is very cool for drag racing but can all but eliminate towing capability. There are pros and cons to both setups but having done centrifugals and turbos I would have to vote turbo as my favorite. Overall though, forced induction in almost any form is great