I relocated the springs 3.5" (from 43" center to center perches to 36" center to center perches) on my '71 Demon and moved the tubs in to match it, and the rear seat dropped right into the car with a little massage work on the tubs.
On mine I just heated them a little bit and used a piece of scrap exhaust pipe as a "roller" to create a small preformed style indentation to clear the seat
