Yea they just need to make more for kjs I mean when I first wheeled it I was really surprised by what a kj could do. I had an offer from a guy to trade it to him for his wife an in exchange he'd trade me his 90 wrangler that he had 350 motor 35 tires and he extended it 22 inches. If he did that would it not be the same length as a 4 now?
It'd be close. A JKU is 116", YJ is a tad over 93". The YJ would be just under an inch shorter in wheelbase. Either way, that's a huge wheelbase on a YJ. You'd think they'd put it around 104-106" like the KJ/KK respectively.
Anyways, before you jump into anything do some research on the stock axles and their limits before wanting to jump to big tires.
Stock the KJ comes with a dana 30 front diff. It's aluminum(I believe, I'm a KK owner). Lowest you can go for gears in it is 4.10s. The rear is a Chrysler 8.25. I think those are limited to 4.88s.
Jeepinbyal sells a steel dana 30 front diff for the KJ. That costs a pretty penny, but gives a stronger housing and the ability to gear lower(I believe that's limited at 4.88 as well).
Stock gears on a v6 are 3.73. You can run them up to 245/75-16(just about a 31x10), but regearing to 4.10s will put you back to stock. If you went with 32s(265/75-16) you can deal with 4.10s, but 4.56s would be preferred.