68 Barracuda shoulder strap question

I have a 68 Barracuda formula s car that I received with very little interior parts. I have no idea as to whether or not it had shoulder straps with the seat belts. It's a deluxe interior car and I wonder if shoulder straps came standard with them, or they were an option. Does anyone know if that's correct or have any ideas as to clues in the car I could look for to figure this out. Thanks, Lou