Im going to need some new tires soon and I would like to get rid of my 31's and put on 33's. I only have a 3.5 in lift and Ill get better wheels to offset them more.
-how much higher do I need to go
-or how much fender sould I trimm
can I see some pics of your cherokee and its 33's

 

You could get 33's on with a lot of trimming, could add 1-2 inches and tim a little to none..I have close to 4.5" of lift and plan on putting 32's on. Bigger then 31's but not quite 33's...

 

33x10.50 or 33x12.50?
10.50 will work fine with stock wheels, and minor trim.
12.50 will want aftermarket wheels to allow good turning radius and a little more room when stuffed, but will require more trim.

either width is going to want same bumpstops and longer steering stops.

33x10.50's, stock wheels, and 2.5" lift...

 

I added slightly longer bumpstops, also turned the stock steering stops out about 3 or 4 turns. And changed the lower CA's from the stock style to the round RE ones. The tires rubbed on the stock lowers due to the Inverted-U shape.

I trimmed around 2 and a half inches out of the front fenders and about 2 out of the rears. I'm using a 33 x 12.50. But I have 8 inch wide wheels with a 4 inch backspacing.

This is after trimming the lower edge of the front the first time... I needed to go back and trim some more.

 

Try this link for some pic's https://www.cherokeeforum.com/f59/xj-lift-tire-setup-thread-260/...Tj

 

anything is possible with a grinder and sawzall