1968 Imperial Build Sheet We removed the rear seat cushions for cleaning. There was the build sheet in the springs. The floor is solid. The build sheet removed from the springs. This is the most pristine build sheet I have found. A close up of the top half. Click to enlarge. A close up of the lower half. Click to enlarge. Look at the code 558 -- that was used on the Mobile Director coupes. They were available in 1967 and 1968 only; very rare. The rear seat upper cushion, cleaned and treated. Ready to go back in. The rear seat back in.