I removed the stock seat in favor of a OMP "King" one piece side mount fiberglass.  I couldn't use the stock slide rail.  I tried the slide rail from OMP but the bolts were too small and larger ones would not fit on the OMP rails.  I used OMP's aluminum side mounting kit (666LE.)  You will have to drill some holes in the kit to match it up to the 4 holes in the floor.  There is no need to use the stock spacers.  The two outer holes go straight through the floor to a lock nut under the car.  The two inner holes have bolts that screw directly into the frame.  I replaced the stock bolts with shorter ones because the stock spacers weren't used.  The seat and mounting kit were purchased from

Driving Impressions
5-B Hamilton Buisness Park
Dover, NJ 07801

The picture below is not that good.  I used a Polaroid, time to get a digital camera.