I've done a lot of reading on this so I can source parts for a disc axle swap on my Mighty Max. The good news is, most of this stuff looks to be interchangeable as long as you stay within the same axle size. 4 cyl 8", 3.0 V6 9" and 3.5 V6 9.5".

I bought an entire leaf sprung, 9.5" locking axle from a 99 Sport. The internal parts from that all interchange with the 3.5L, 9.5" coil sprung axles.

ASA shows the pre-2000 3.0 Sports were also available with locking diffs. They seem less common than the 3.5s, but they're out there.

The differential carrier and the actual locking diff are common to both the Sport, and the full size Montero. ASA shows the part numbers are the same for K96W / 3.0 Sport and V43W / 3.0 Montero. So you should be able to pick up a carrier assembly from either truck and be ok.

The axle shafts are specific to the locking diff and the Sport. They're different right to left when you have the locker. The part numbers don't interchange with the full size Montero. That doesn't necessarily mean they won't fit, but it looks like you'd be taking a shot in the dark here.

I've looked for 3.0, locking Sport axles. They're uncommon and expensive. The extra effort to get the 3.5 axle to fit was an easy trade off given that I can actually find those.