3.73s and 31s are about your limit. My 90 with the 2.3 and 5 speed on 31s isn't a speed machine with 4.10s. But around town and on the trails it did really well. With the pending SAS and sitting on 33s, it won't be anymore fun on the road, but ought to be good for what I need in the dirt.
Good starting point. Swap those tires soon, so you can have some traction in the dirt. I'm cheap. I watch my local forums and get some stellar deals on stuff now and again. The 33s? 1/2 tread BFG Trail T/As, still good though older tires. All 4, on rims I can't use, plus a spare 32 generic mud tire also on a rim... $20... I've got two sets of 35s, one set will pass safety, the other is only good for spares. Both for free. I have some other 33s I got free also. I got a parts Jeep for free (axle for my Ranger SAS), great tires for my XJ. All I'm saying is, hook up with some local wheelers. They might have decent tires they'll let go for cheap... Or free.
Post some trail pics!