Sparco r100 passenger seat into a 78 280z went in fairly smooth. Needed to drill new holes for bolts onto the seat mounts because the rails are now wider apart with the sparco seat. Ok so more details now that both sides are in. I did not bash my trans tunnel to get these in. Not bashing it does leave you a tad bit off center from the steering wheel. I may go back later and bash it in if I want to be more centered.
I used the stock sliders and left the front screw hole alone. You do have to drill another hole about an inch or so further up in the rear of the slider to fit the screw to the seat bottom. That part was pretty easy.
On the the passenger side I was able to use the door side floor mount holes and bolt it in and then made new holes for the trans tunnel side because it is further apart.
On the driver side I used the stock floor mount holes that are toward the trans tunnel. then I made new holes in the seat to floor bracket closer to the door to fit the new wider base. The seat does rub against the quarter window weatherstrip in certain positions. (something that can be fixed with bashing the tunnel). I can use the sliders to there stock limits..
i would say give yourself about 2-3 hours to swap the seats out, measure everything and start drilling. Again the only modifications I had to make were new slider to floor mount bolt holes on one side front and back per seat and drill holes in the sliders for the rear slider to seat base screw.