I currently have some 2nd generation RX7 seats in my '72. They weren't a direct bolt-in, the rails were spaced differently. I took some 1/8" by 2" steel strips, cut holes in them to match the holes in the seats, then more holes to match where the origional seat rails fit then bolted the whole mess together. The passenger seat was more difficult - the left rail was higher up and at an angle, so I had to create a spacer to mount it to the strips.
I recently found some mint '85 Z seats and will be putting those in instead because they're cleaner and should mount up a little nicer. The RX7 seats are very nice, though. They support my back MUCH better than the stock 240Z seats did.