33's are most commonly fit in two ways on TJ's:
1. 4" suspension lift, with ~2" bumpstop extensions in front and ~2-2.5" in the rear. Requires a SYE/CV shaft.
2. 2.5" suspension lift, with a 1.25" body lift, with ~1.25" bumpstop extensions in front and ~1.25-1.5" in the rear. The 1.25" BL usually accompanies a 1" Motor Mount Lift to offset some of the driveline angles.
Either way you go you'll also need to check full bump, full flex and full droop and figure on many of the following components: longer front brake lines, extended sway bar links front and rear, gears, brake and steering upgrades to accommodate larger tires, SYE, CV shaft, bumpstop extensions, new shocks, adjustable track bars, and a rear track bar bracket.
Here's how I ended up fitting 33s