On these earlier trucks, ADD and manual hubs are essentially the same. ADD has splined flanges that engage the axle and the sliding passenger side stub axle to disengage the diff.

IMHO, ARB locker does A LOT to prevent damage to the small front diff. Since you have pure traction, you can take obstacles slower and the wheels won't spin up when they leave the ground like they do with an open diff or LSD. You DO need to pay attention if the wheel may be bound up, but that situation is a lot more controllable than the wheel off the ground situation...