Basically the seats used to be mounted on wooden risers which had a recess in them to take the bolt Dave mentions. When the factory lowered the seats to accommodate the revised dashboard height they did it by the simple method of deleting the risers and bolting straight to the floor. Which stresses the rails over the bolt (there is no hole in the floor to take it) which means the seats won't glide properly. A few spacers should cure it....or cut a hole in the floor and seal it from below when the seat has been fitted.
Nick

Last edited by nick w; 18/03/19 03:36 PM.