I had 31s on my 1998 XJ that had the OME lift with a 1.5" spacer. I had issues with the 31s rubbing on the swaybar at lock.
Also check your bumpstops at stuff, at one point when I was running 30's with a 1.5" lift, at stuff it would pull in the fender. Make sure that you check ouor bumpstops(I used a hockey puck).
Looks like you have a pretty nice XJ and have good plans for it. Also note that 30X9.5 is probably the biggest tire you can fit in the stock spare space. Look into a rear bumper with a spare carrier.
Attached is a pic of my old XJ.
Hope that helps.
2k5 TRD TacoDC