Mike,
I think i understand the books numbers now. ( And why i think that are so low) the numbers you show are for GT trim convertible only. Does not account for GTS or other trim levels that were Convertible
I added the GTS numbers above, still not many Dart convertibles built in any year! The Galen White Books cover all muscle car years, there are about 10 books total, even come in large print for us old guys...