There is no real benifit to swaping the axles except that the ZJ 35 with had disc brakes. You will have to cut off the coil mounts and weld in leaf spring perches...which is way too much work for a dana 35. You are better off lloking for an XJ dana 44, which is way stronger and is a direst bolt in.
The front, there is no benift at all. they are the same diff. Some ZJ's came with CV joints, which was very bad...watch for that.
Talk to bogjr on here...he has a dana 30/44 combo with 4.56 gears and a detroit locker in the rear, which would bolt right into your XJ.
They are hard to find, and even harder to find done up like that...so I would certainly jump on it.
The t-case would fit, but I see no advantage, unless yours is pooched.
Smurf.