1988 and up 4 cyl Rangers had Mazda M50D-R1 manual 5-speed transmission, 2WD or 4x4, only difference was an easily swappable tail shaft housing for transfer case hookup.
While trans will probably need to be pulled out to repair it, if your shifter bushing are really bad, lots of play in the shifter, then you may want to pull it out and have a look.
How to here: http://www.therangerstation.com/Maga...bushings.shtml
Above Step #9 is a picture of the 3 shift rails, only 2 are seen easily in that picture(they are in neutral position), each has a slot that lines up with the other 2 when trans is in neutral.
If bushings are worn out shifter can go over too far and not move 2 shift rails like it should and trans gets locked because shift rails are out of sync.
Try to line up shift rails for Neutral you sometimes need to rock the truck(move driveshaft) to release pressure so shift rails will move.
Most likely you have a broken part, but you have to pull the shifter anyway to get trans out, so worth a quick look.