Reply to "New seats"

Whatever you use for this, be sure the things fit flat and is stiff. If the rails are not positioned flat, they will twist or pull down at each end, and you'll be calling your neighbors to help you 'adjust' the seats on their sliders. Bolting adapter strips on top of the carpet will bend them, producing a lock-up of the adjusters. The seats should also be higher in front than in back, which was part of the function of the little dual-size aluminum spacers that went through holes cut through the carpet to rest directly on the steel floor. I suggest keeping them and drilling a pattern for the stock mounts and a second one for the new seat rails.