things to be aware of with zj's are: the rear dana 35 sucks for serious use, axles and spider gears are usually the first weak spots you'll find. 4.0's are almost indestructible, don't be scared of higher mileage with these, but they will seem underpowered in a zj with more than 31's. lifting them isn't too bad, but once you go past 3", control arms, track bars and steering linkage angles will be an issue.
if you're talking v8's the dana 44a rear is ok for the power, but doesn't react well to twisting the housing up off-road and upgrade parts/lockers are limited. also, the all-wheel drive transfer cases have a habit of tearing up viscous couplers at the wrong time and get expensive to fix. the v8's seem to do ok reliablity wise, but don't expect great gas mileage. shop around for zj's, according to the book values they aren't worth near what some people are asking (should be able to find reasonably good shape under $2000).
depending on how much room you need/want, i'd probably lean towards an xj-some came with dana 44's or chrysler 8 1/4 in the rear, if they didn't, the rear leaf setup is much easier(cheaper) to swap a ford 8.8 into; the xj's power to weight ratio, narrower body and shorter overhang also work better off road.
