By removing the seat rails and mounting the stock tracks directly to the floor pan, you can install Recaros and Momo seats. The stock back pad seat cutout needs to be widened by opening up the seam, taking out some padding and then re-glueing.
The Recaro mount/slider has 90 degree mounting rails with 3 mounting holes. I attached the front ones to the boxed member by drilling horizontal holes thru the member and using long bolts. I then bent the rear rail mounts horizontally and mounted them directly to the floor. This lowered the back of the seats providing great helmeted head room.
Being a bit on the "manly" side (5'10" and north of 200lbs), I found this far more supportive and comfortable than the poorly padded narrow fiberglass stock seats.
