What are there differences in the seats and dimensions between a 91-92 fj80 vs the later fzj80?
Biggest difference that I'm aware of is where the seat belts mount. For 91-92 the female end of the belt mounts to the floor independent of the seat. For 93-97 the female end is mounted to the seat itself, and needs to be incorporated into a replacement seat/bracket.
Mounting to the floor for all 80 seats should be the same.