'65 to '67 call out C4ZB-7666700 spring assembly. '68 calls out C8ZB-7666700.
Date on '68 FAM drawing is 11-7-67, superseded 5-11-67. 67 drawing is dated 6-9-66. A drawing rev sems missing (maybe many) but as the seat backs added the deluxe emblems a change for that is required (and noted).
Just noticed the number change and got curious...