Most stock wheels are 15x7 and a 33"x12.5" will fit. The sidewall will bulge more than if on a wider wheel, and you'll run less air pressure than you would on a wider wheel. An 8" wide wheel is most common for that size tire on a jeep.
You will run into clearance issues with the tires rubbing the lower control arms when turning, and possibly rubbing the upper spring buckets in the rear when flexing. Wheel spacers would help if you're wanting to keep stock wheels.