Check that VIN again. Looks like you got an 83
H/O with a sand gray interior. To which, sand gray was never an interior option for 84
H/O, regardless of what the early ordering information showed.
Sounds like a couple of possibilities- the push buttons aren't adjusted right on the shift cables to allow the buttons to be pressed down far enough to get it into reverse, or something else could be jamming them up. Without looking at it or observing the operation, it'd be tough to make the correct diagnosis. Whatever you do, don't force it, you'll break the little tabs on the bottom end of the shift detent release. Some of the detents you need to press the button down completely, others you can just depress it slightly.
When they operate correctly, Lightning Rods are cool AF. But when they're misadjusted, or broke, they're a huge PITA.
If you need shiny new black knobs, I got them.
88hurstolds rebuilds them. He may know what's going on with the issue without even looking at it. But send him a PM, he can help you out.