31s will work fine on factory rims on a stock height 4x4. they may rub on the control arms at full lock, but there are ways around that (adjust the steering stops or swap in WJ lower control arms). if you go with aftermarket, get the most backspacing you can get. stock is around 5.25".
for a 2" lift, you can get away with poly pucks up front, and then either longer shackles or an AAL in the rear. for 2", your brake lines, shocks, and steering will all work ok. you may need to adjust the steering though to fix the alignment or to center the steering wheel.
my 4x4 90 with 15x7 Canyon rims (from a ZJ), 31" tires, stock height and WJ lower control arms.