Okay, I went to the shop. As the hood closes it shifts toward the driver's side. It lays flat, but there's no more adjustment to the right. When you watch the passenger hinge in particular you can visibly see it arch toward the driver's side on the way down. He said when the hood/spring isn't attached the "rivets" are loose.
So, this is what I've found on my car.
The dash date stamp and door seals are January. Engine cast date is February. The two existing hood hinges are dated OB 3 17 2 and OB 4 7 3, but of course, I don't know if they came with the car.
Anybody's guess on the appropriate range for the hinge dates?