Updating a 64 Dart vert

OK... My 68 is getting a bucket seat interior from a 67 parts donor car. It has some pretty cool looking headrests on the seats.

My question is when did they start putting in the shoulder belt on the fish? There is a bolt up there where it might attach. Around here the broke cops have been handing out seat belt tickets if you do not have a shoulder belt showing even if your car did not have them. A hot rod fish is already cop bait and I want to geive the cops less excuses for pulling me over.