Ford/Mazda installed 7.5" or 8.8" differentials in these trucks
All 4.0l engine trucks got 8.8", that started in 1990
3.0l engine could have either.
And Limited Slip was an option on either size, so you first need to know what size differential you have.
Ford calls their Limited Slip differential Trac-Lok, GM calls theirs Posi-traction
Both use clutches that will "slip" when cornering allowing wheels to turn at different speeds.
Both also need additives to allow this "slipping" or clutch plates will shudder.
Any "auto" locker, like above, will be the same, 3rd party cost more and tend to be better, but there still isn't positive locking.
Then you have manual lockers, these are manually activated, these act as an open differential until you turn them on, then axles are locked so no going around corners on hard surfaces, lol, but you will have equal wheel power on both wheels when locked.
With a 2WD truck I am not sure what you are after in the end?
If you need both rear wheels locked while going in a straight line then manual lockers are what you want.
If you will be driving on slippery roads, i.e. snow/ice, then auto-locker might be better choice, and rebuilding your Trac-Lok might be best option, or a Detroit Locker