Fit is a relative term. It entirely depends on what you use it for.
I wheel mine moderately hard, flex a lot, big rocks, tight trails.
Use stock wheels with 1.25 spacers or 7" wide wheels with 3.75 backspacing. with 33x10.5s. 8" wheels with 12.5s can work but it is harder. I know.
I cut and folded the rear half of the pass side rear wheel lip, (behind the tire inside the wheel well), or the tire will catch it and cut it up like I did. Driver side not an issue. No bump stops required in back if you have a stock axle. it will tuck a 10.5. With the narrower 8.8 and 33s they will tuck a 12.5" in the wheel well lip barely.
Cut the front fender about half way up the stock stamped flare of the fender.
Remove front inner fenders. It works good but all the crap that flies off the tires now gets in your door hinges. A minor side-effect.
Cut slits in the pinch seam at the rear of the front wheel well.
At the front of the front wheel well, trim and trim the obstructing inner fender support as needed, but no more.
Bump stop just enough so the tire doesn't grab the fender or inner when the tire is all the way up in the wheelwell. I used 2 hockey pucks RTVed, plus the factory stops. Don't laugh, work perfect and cheap!
lift it 3-3.5" any less will hit the accurate bump stops just hitting street bumps. You would have 2" or less of up travel. You can get away with less lift if it is a pavement queen or you like a crappy ride. I am picky as all hell and it took me 4 years to figure it out.
In my 9 years of wheeling, 31s with stock gears will almost always go were a rig on 33's can but the guy on 31's doesn't need new gears, a new rear axle, or to chop the hell out of his rig. I have no regrets, but it would be easier to stay on 31s.
98ZJ, 4.0,242, 8.8 Detroit, hp30, 3.5" lift, IRO LA's 4.56's, 33" Firestone MT's, custom rear bumper, ARB front, Engo E9000, factory skids
My driveway build here: http://www.jeepforum.com/forum/f197/spidermonkey-s-98-zj-build-716209/
speedo reading x spd gear tooth count/gps speed = new spd gear for dead on accuracy
North Shore Wheelers www.nsw4x4.com