Welcome to the forum fire_craft. To run 33's you will need a Superlift 6" suspension lift (very expensive) or the MML which is a 2" body lift, 1"-2" t-bar crank, new rear spring pack or lift shackles, wheel spacers, and maybe some fender trimming/massaging. A new spring pack will increase the bed weight capacity and also improve towing heavy trailers. For more hp and tq you will need a good air intake system like Spectre, K&N, AEM, a high flow muffler like Flowmaster, Gibson, Magnaflow, a handheld tuner like Hypertech, Jet, or a custom tune from PCM 4 Less, Wait 4 Me, etc. Converting to electric fans can also free up some hp. Headers, higher lift rocker arms with matched springs, and a larger throttle body are some other ideas. Removing the airflow restrictor on the throttle blade is a great "free" mod that makes the throttle more responsive. To make even more power you could add a supercharger or swap in a V8. Some other good mods are upgrading the lousy factory shocks to Bilsteins, and upgrading the factory rubber sway bar bushings and end links with Energy Suspension polyurethane bushings.
We have all done pretty much everything you can do to these trucks so read through the topics for more info or ask if you can't find something.
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*