Not so fast. Using SR 3rd member requires using it's axle shafts. I believe you can mate those to leaf axle also gaining additional benefit of disk brakes. MSport had drum in rear on leaf axle. So the easier would be to find MSport Ltd 98-99 axle with locker already. Again it will have 4.272 ratio so you would need to either source 2000+ 3rd from MSport XLS or Ltd (they both had 3.5L = big axle and 4.9 ratio) then swap the gears or get new set from dealer.

92 SR, 285/75R16 Yoko MT ARB locker GAST compressor AirLift 1000 MM10500 Snorkel custom rear bumper
02 Montero LS died protecting the master
08 PowerWagon (stock!)