SR Gen2s could have a rear locker from '92 on, but it seems pretty rare on the earliest of the Gen 2s, not a popular option back then. The 3.5 liter for USA made its debut with the '94 SR Montero. I still have a 4 wheeling magazine from 1994 that ran a head to head comparision on the new 3.5 liter equipped Montero and a Range Rover Classic.
Hope this helps you out.

'92 SR Montero, Green, with 31" Yokohama Geolandar A/T Plus Tires, Mitsu factory fog light kit, on-board air compressor,Sony Radio and 10 disc changer. 213K and counting.....
Stock & Happy otherwise