Yeah, I'm not a full resto kinda guy, but would like to stay with something original looking, maybe I'll try and find a set of retractors and buckles and just leave the shoulder belts stored up there above the windows.
If that works for you. I was just running lap belts on my Challenger, but I decided I didn't want to eat the dash if someone hits me.
The only real difference with the modern belt is that you always have the belt running up to the roof mount, so you can't tuck it out of the way. That was the part of the old set up that I liked, being able to tuck the shoulder strap up on the roof. Gives you an unobstructed window for pictures. Really shows off the hard top aspect of the car, no seat belt hanging down in the way.
But I drive my cars too much to trade safety for the aesthetics of not having the seat belt hang down from the roof.