Tracks definitely changed every time the floor pan changed. Sooo,
I know the early A bucket tracks are totally different from 2nd gen' A.
I know they changed again when the right floor pan changed for Cat' converter ( 74 or 75 ).
Will 67,8,9 low back bucket tracks interchange with 70 through 74 high back bucket tracks ? I can't answer that one.
I can add that the track materials did change between 69 and 70 so their parts are not interchangeable.