68 and up has shoulder restraints and latches on the seat back hinges. That belt across the chest would hurt a lot more if the seat back went forward with you.
Yeah, that. The loose seat back is kind of dubious used with shoulder belts. But you probably don't have shoulder belts in your 67 so you're good. I'd go with the 66 seats for the look and try to make them work with the 67-69 tracks.