There is no way to install locking hubs on Gen 3. No easy way at least.
4.3 is for 5speed and 4.9 is for 4 speed. 4.9 are direct replacement for 4.3. You can get new R&P set from dealer or just get complete set of diffs from junk yard. They are bolt on.
Not sure which oem manual you are looking at but mine is pretty clear on that.
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Now I'm thinking there used to be a typo in printed manuals subsequently revised in TSB.

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!)