You would have a Dana 44 Twin Traction Beam in front. In back, it's probably the 8.8" Ford, but a 9" is possible. The 8.8" has a removable cover, 9" doesn't. Look for a tag on the diff for the gearing, or just post the axle code from the door jamb sticker and we can decode it. That's assuming the gears are still factory.
Yeah, that's what the twin traction beam (TTB) is. I guess you could say it's a D44 chopped in half that pivots at the center. This setup was used from 80-96 on 1/2 and 3/4 ton trucks, except heavy duty 3/4 tons used a Dana 50 ttb.