Just to clear some things up here, I cant stand it when people start bashing the D35. Most of the people that say, "ITS GOING TO BREAK, DONT PUT A LOCKER IN IT" have never even had a D35.
YES, you are right, D35's are a weak axle when compared to a D44, D60 ect. However with only 31" tires, and more than likely an automatic (sence this is a ZJ) he should be fine.
Carry some spare shafts with you just incase. But just remeber not to romp real hard on it. I ran Lock-Rights and Aussies in 2 D35's for about 4years, my set up was on a '93 YJ with 4.56 gears, 33" MT/Rs on steel bead locks (HEAVY) and I only broke one axle shaft, and guess what I was doing?.... Foot to the floor, rear axle hopping, going up hill pulling an other broken down Jeep. Luckly I was carring a spare shaft, I swaped it out and was on my way.
As for street driving, the act like any other full time locker. You will hear the teeth "ratchet" going around some turns, sometimes you will have the inside tire chirp a little.
Again, with an automatic it is MUCH MUCH easier on the drivetrain. You will notice the locker much less than on a manual trans
In the end I highly recomend luch box lockers for a D35. You can easily install it yourself at home, and unlike a full case locker, you dont have to dump a whole bunch of money into your D35 to have a shop reset up your gears. A few years down the road, or perhaps once you DO break your D35, you can start looking for a XJ D44 or an 8.8.
BTW Super 35 kits are pretty stout. I installed one into my buddies TJ who has had zero issues with it. He runs 35" MT/R's on steel wheels, he runs the Hammer trails every weeked during the desert season. Never broken it.
