80-82 tases were the standard mechanical part-time NP208's and the optional mechanical full-time NP219. In 83 the 219 option was dropped for the vacuum NP229 along with the added vacuum shift D44 front axle (83-84 only). It's easy to spot with the vac motor sticking out of the diff cover. The 229 case is "similar" to the Eagles full-time case NP119 but the 119 has no low range mode. On a new to you 83 it wouldn't be a big surprise if the 229 has been previously swapped out for a 208.
"Don't mind me. I'm just here for the alibi"