31's are the largest tire you can fit stock. Therefore the only reason you haven't rubbed (noticeably) yet is because you haven't wheeled it yet.
Best bb in my opinion is some 2" spacers, good shocks that are 2" longer than stock, some 2" bumpstop extensions, and 31x10.5 tires. It'll look good and give you a little more ground clearance but avoid driveline troubles and retain stock wheel travel (as long as you get longer shocks).
1998 TJ, 2.5" OME springs, OME N66 & N67 Sport Nitro Shocks, 33x12.5 Goodyear MTR's, Metalcloak front trackbar, JKS rear trackbar, Metalcloak aluminum front arched fenders, Metalcloak aluminum front bumper, thedirtworx tire carrier, Warn xd9000i w/ synthetic line and TRE Safety Thimble II, Monstalined interior