My 96 Ranger 4x4 has 4 wheel ABS. It is not super common, but does exist. Yours should have rear wheel ABS at the very least, I believe it was standard by 97. I have seen a 95 Ranger 4.0 4x4 with 4 wheel ABS as well.
How to tell if you have ABS:
On the rear axle: look on top of the differential. There will be a sensor bolted into the housing that reads a tone ring on the ring gear. You will see a wire loom coming from it.
On the front axle: Your front rotors would have tone rings (toothed cogs) pressed onto the back side of the rotors, concentric around where the inner wheel bearing sits. You would also have wheel speed sensors in your steering knuckle, which would have wires coming off them, that clip to your front brake hoses.
I have found varying causes for rear wheel lockup:
Bad or damaged sensor on top of the differential
Leaking or sticking wheel cylinders (they should ALWAYS be replaced with the rest of the drum brake hardware, in my opinion) - this has been the most common cause for me
Leaking wheel seals; it defies logic but in my experience if a wheel seal leaks enough, the gear oil on the pads causes lockup (im guessing due to swelling)
Cheap shoes: certain times of shoe pad material are super prone to swelling as a result of moisture in the air and will cause lockup. I have had this happen as well. I believe this is a common problem with cheap organic pads the worst
I'm assuming you changed adjusters? Though I have never had them specifically cause lockup for me because usually if they are badly rusted, they just won't move at all and then just cause uneven shoe wear
I know some of those things sound odd but they have 100% been problems on several Rangers and other vehicles I have, which identified through replacing parts I suspected to be the cause one at a time.
Also, is your ABS light on on the dash? If you have ABS and it recognizes a fault, that light will be on. Not saying this is a sure fire way of knowing if there is an ABS problem, just would indicate one if its on