I would have to say beside some of the more exotic options LO23 & BO23 Cars or M code A-bodies the 72 foldable fabric moonroof would have my vote as a rare option. I saw a defrost option about 16yrs ago on a Duster we used for parts. I currently have a 73 H Code Sunroof Dart for what that worth with light Parchment interior. Any one ever seen a Savage Barracuda? If there is one still out there, it might be the rarest of rare A bodies, even though it wasnt a factory option or factory backed race car, still a cool car not allot known about!