I think the automatic hubs are the same from '83-'97
They often failed to engage when needed, which is why someone changed your truck to manual hubs.
The first few times they don't work can be frustrating, because you NEED 4WD only at the time they fail, lol, that's how you find out, the dreaded "click, click, click" of "almost engaged" auto hub, and of course no 4WD.
And then there is the "bump" click, click, click, if you hit a bump/pothole just wrong one hub would try to engage, so click, click, click, you needed to stop and back up 50ft to disengage.
That is the normal procedure for auto hubs, after using 4WD use button to shift transfer case to 2WD then back up 50ft to disengage auto hubs, usually 10-20ft was fine.
Knowing the above I wouldn't recommend the switch back to auto hubs, but choice is yours, I doubt you can buy the parts new any more so best bet is a wrecking yard.
This link shows how to switch from auto to manual(just read it backwards) so you can see the parts needed: Automatic To Manual Hub Conversion
I am sure you could also find some one here or in your area that would do a swap with you, maybe do all the labor just to get manual hubs, lol.
You can just leave the manual hubs locked during winter or when you think 4WD will be needed more often, and just shift transfer case when needed, won't hurt anything, small hit on MPG but not that much, .5/mpg maybe
All Rangers from 2001 and up had front hubs engaged 24/7, no way to disengage them, just shift transfer case from 2WD to 4WD