depends on what your going for if your after bolt on and go id say magnacharger. if you want to spend a little more time tuning it for racing and so on id go procharger. i can get you a deal on either one. dont go whipple, until they come out with a intercooler id wouldnt buy one. dosent look like there coming out with one for the 5.3s either acording to my buddie that works there.
old set up: 2002 chevy 5.3, procharger 12lbs boost, asm headers, ls1 edit, flames, 20inch budniks
New Set up: 2004 chevy 5.3 ext cab, 12 inch twisted suspension lift, 36's, exhaust.
future mods: 150-200 shot, ls1 edit, air intake, stall, 5.13 gears, 12s or bust