You should check with ARB to see if the locker will work. If you were swapping out to the lower 4.88 gearing, you would have to swap out the the factory ring carrier.
One option you didn't mention is to swap out your D30 with a high pinion version from a 95½ to 99½ XJ. The high pinion version from that era uses stronger u-joints and has reverse cut ring and pinion gears. Reverse cut are 100 times stronger due to the physics of how they rotate. If your ARB can be ran with the 4.88 gears, it will fit right in to the HPD30. All you would need to do is run the air line.
FYI, the D30 and D44 use the same outers and axle tubes. If you jump your Jeep a lot, then I'd worry about bending the tubes. Most bolt on axles trusses made for the D30 will beef it up enough to keep it from bending under normal use.
One thing to consider with the D30/D44 is that running 4.88 gears, the pinion gear is tiny. Running 37's, it will be a weak link and will probably go before the axle shafts will (if you are locked and crawling). If you get stupid with the skinny pedal and spin the massive amount of weight from the 37's alot, then you will surely break the shafts. A super kit with cromoly shafts will increase strength, but the possibility of breakage while spinning the tires is still there.
BTW, I did a high pinion swap on my TJ. You can read the article I wrote
by clicking here.
Cheers
What to do with front dana 30 diff?
