First, there were two options for the shift: shift-on-the-fly and stop-and-shift. It sounds like you have stop-and-shift, but please confirm 1983-1984 is a transition and AMC made it's updates running, not by model year. The switch will be labeled.
This determines the front axle assembly you have.
Once you know that, you'll need to assess any modifications you have. The front axle shifter, if equipped, may be locked and the transfer case may be held in 4wd with a spring or cable. However, it may just have had all the vacuum lines re-routed. In either condition you'll have to have rubber vacuum line, nylon air line, and an appropriate vacuum diagram before you start.