I would guess that the seat is bolted down. The FC and FB have a clever system that mounts the inboard rail a couple inches higher and on an angle with the trans tunnel. This makes it almost impossible to mount a seat properly, as the Adjustment is built into the seat frames mounting.( stock)
When I put the FD seats in the FB I ran into the exact problems as he did. The seats are just not dimensionally close at all. IMO. The bottoms of the seats drop down low which in turn causes the higher seating. For me at 6'2 that doesn't work well in the FB.There is o way I can get my helmet on and fit inside the car. I found that S4 seats are a direct bolt in on the passenger side. The donor car I used did not have drivers side seat rails so I made the FB rails work. I have come to hate installing seats
