Seatbelt question: What year required shoulder belts?

Yep. I been rocking and rolling on my sons 69 notchback. Last 3 pages of his resto thread, we are really starting to make progress.
Haven't really done much, Wisconsin winter without a heated garage, and a kid in hockey kinda keeps me out of the garage. I did get a replacement a-pillar and rockers for it. The rest is just planning right now.. but it's February and I'm getting itchy to get greasy and patching bloody cuts. :)