Pull up the carpet over the RR wheelwells facing the RR - if you see the captured nuts it’s possibly a quick plug / play deal.
A ‘96 cab might have them where the older they get the less I’d bet on it - but ‘96 is new in the big picture of 80’s.
Triangle pattern about 3” in between the holes...
Big tip-off is if you have a triangle of captured nuts under the carpet in the RR wheelwell facing the RR.
If not, then prob no captured nuts for the outboard 3-point seatbelts in the RR pillars.
If you don’t have those to start in the cabin, this is going to get involved compared to...