Wow, when it comes to these seats you're like an encyclopedia! These particular seats are for a friend and I don't believe he's that fussy to the exact date since this isn't an original H code Duster that's he's building for his daughter.
I'd love to talk with you since I have a pair that I want to make work in a 71/72 Demon clone and I'd like to know what I have and how to make the 71/71 seat covers work. I can send pics, but I know they have a lift button on the side which tells me they must be from a later model A body. I say 71/71 because I have determined if it will be a 71 or 72 clone. It's currently a complete '72 /6 with a bench seat.
Where are you located?
Thanks
Todd