Just fyi...
the middle seats should be a direct bolt-on.
the front seats, I would imagine would be too, but I'm not sure about the electronics.
does your 91 have electric seats or are they manual? the front seats on the 97 FZJ80ss, specifically, the leather seats were electric (unless they were converted in port or by dealer to leather)...then they'd be manual.
having said that, if you do have manual seats and you know for a fact that you have the electrical plug already in place for electric seats (I don't know if Toyota provided electric seats in 91/92 model years), then it should be fine.