Stiffening, cage if you feel froggy, proper bumpstops, and well tuned shocks.
That being said, you could just buy a $1000 beater and flog the shit out of it. I did that to my 98 XJ for something like a year, it's been bottomed out on the shocks so many times the bushings came out in pieces, the front pinion/driveshaft chewed a hole in the exhaust, and the steering linkages scratched up the oil pan, and I drive it 140 miles a day for work with no problems. I paid $1000 for it in 2010 and I think I've put something like 700 in junkyard parts on it now to make it look nicer and keep it going.
Stock except for a V8 ZJ tie rod, helper shocks in the back to deal with the saggy leafs, broken-off rear bumpstops, and one front shock (240k on it plus my abuse, so I can't really complain) is completely, utterly dead at this point. Oh and I put a grand caravan radio in it, which helps the suspension a lot.
hell, XJLI has ridden in it while I did some of this, I came out of that run with scratches and scores all over the bottom of the gas tank and then drove it home.