A case of use what you have on the production line for sure. Pretty common.
My 1973 was a late 73 H Code thet made plenty late duster-dart 340 cars. My car has some 74 parts on it. It was almost all orginal old man car, bought new in New Orleans. Died and wife drive it to food store, church etc. Their son took it away and sold it, when she was no longer able to drive safely.
I know the guy who bought it from them and I am 3rd owner.
