Well my 98XJ is pretty much proper built at this point and does almost everything I want it to, but I feel like I've had to make a few compromises due to the uni-body.
I've got an 05 5.3L/4l65e and a hybrid 231 case, lots of plating and bracing, built 30/44 axles that have never let me down, on locked 35's. It goes wherever I point it, better than any XJ's I've wheeled with in my area. It climbs like a muthafucka due to the weight/traction, and it's heaps of fun on the street as well.
The problems:
1. The COG is higher than I like. It's fine for climbing straight up/down stuff, but side-hilling sucks. I could solve this partially with front/rear anti-rocks, but then when I go to add a cage, I'd end up right back where I started. I need the cage to safely side-hill, but I also need the cage, which makes me just as likely to roll over even with the anti-rocks.
2. 98+ interior sucks a big-ol-donkey-ball. It's like I'm driving a neon.
3. HVAC is toast and a tonne of the kind of work I just don't have the motivation to do.
4. Still needs more bracing. The Durango box powered by the chevy pump is an awesome combination, but once I plated the frame around the box mount, I started blowing through sector shaft bearings. I could build a sector shaft brace, but as with everything, that's more sprung weight I really don't need.
5. I still need to do a lot of work to the rear wells to clear the 35's. With the largest cut/fold possible, 35's still bind at the front/rear of the wells. I need to comp-cut to fix this. Plus I'd like to move the rear axle back a few inches, which would mean relocating the fuel tanks up higher, which again, increases COG.
Most of my issues come down to "everything I need to do results in a higher COG", unless I throw some tonnes on, and run wider and taller rubber. Yea, I could build a buggy, but the point is that this is my DD so it has to be relatively street legal.
After wheeling with a buddy in his mild built 4-runner, I immediately realized that his truck, despite being several inches taller (his roof is in line with the top of my roof basket, and he's got easily 3-5" more ground clearance than me), is more stable on side hilling due mostly to the full frame and lack of uni-body up top. It's also got better approach angles per inch of clearance despite being a few inches longer. Everything interior is pretty much the same size as the XJ (which is important as I've got passengers and gear to haul around). Just in general, it's seeming like I can sell my XJ for quite a bit more than it'd cost me to build a runner a bit farther than I've got my XJ.
That said, I know practically nothing about runners. The above was all just to give an idea of where I'm at and where I want to be, and I'm looking for input on common problem area's with the runner builds.
I'd be swapping in a 5.3L and 4l65e trans again most likely, which solves any questions about the weak ass stock motor, but I'd like to retain the yota t-case mainly because you can just drop in a 4.7/1 gear. Is this even remotely plausible? How well does a 5.3 fit, and will the extra length of the driveline cause a bunch of problems, or do I just move the CM back to accommodate? Also, can the stock t-case be clocked up if it's moved back, to give additional ground clearance? I know it SHOULDN'T be clocked in it's stock location because of the front DS angle, but I figure if it's moved back 6-8", clocking becomes perhaps possible?
I've heard they suffer from catastrophic frame rust. Where should I be looking on a potential donor? What area's go first?
All the suspension mounts would be replaced either way, so not worried about them. I'd be linking the front for sure. The rear would either be linked or leaf sprung on 63" chevy leafs (like my XJ). I noticed the fuel tank is right in the way for a 4 link. Is there a convenient spot to relocate the tank that won't put it higher than stock?
Are there any other big issues to be considering?