On the RodDoors page link that I provided above, under "Other Applications", it says: "Seats are available in widths starting at 43" increasing in 2" increments up to 59"". Sounds like they can make whatever width you need (within those limits).
Curt ---- 1953 Chevy 6400, 1957 Chevy 2dr Sedan --"Mediocrity is easy, the good things take time"