I've had the Gibson on mine for around about 6 years now. The engine mounts looked fairly new so I didn't change them out; engine has been replaced at some point prior to me buying it with 195k for $700. I've replaced the trans mount with an OEM replacement since I was in there anyway swapping out to a NP242 and it's cheap. I put frame stiffeners on the rear while replacing the leaf spring mounts, front and rear (I hate hidden nuts), and a hitch on the rear but otherwise no additional support to resist twist. Just added a front hitch this fall, huge difference, but off topic...
I'll be the first to admit, if my 94 XJ is in the rocks or mud, it probably has already been a bad day or will be shortly; that's what my 88 XJ is for... I built my 94 for two purposes: Snow and pulling a 2500# boat. Stiff springs, stiff shocks, stiffest OEM sway bar in front and aftermarket in back, no disconnects, definitely not set up for offroading, it's purely set up to tow. I'm not easy on it however; 2,500 lbs on the hook, FT 4wd, pretty much just put the peddle to the floor most of the time... Coming off the boat launch, 2500# 24ft pontoon boat in the drink, FT 4wd, let er rip... The driveway up to the "cabin", in particular, is why I built an XJ; straight up the side of a PA "mountain", 180° switchback, runoff crossing over the lane. My buddies 2wd 1500 can't do it, a 4wd full size does it but you can feel the driveline binding; just put the NP242 in FT at the beginning of the weekend and on a few occasions not notice it until after the 2 hr drive home. There's also another PA "mountain" in between, so 4 full-power jaunts per trip, twice a weekend, all summer long. I'm not a timid driver either, with or without something in tow; I built a XJ to whip around in, with or without a load in tow, not lumber around like a whale. Between that abuse and blasting through the monster puddles that form around here after downpours, no issues yet. Knock on wood.