Definitive source? Ahhh, you give me too much credit!
I can give you some background, if you care to read on....
In 1995-2000 I was working on a pet project/home video. The topic was a sorta ripoff of the Dukes of Hazzard, The Fall Guy and my own life mixed into one. In the feature, I bought and wrecked several cars doing the various stunts that were filmed including the 15 car jumps. I used up several K frames, control arms and wheels. To keep the cars moving, I frequented the self service yards alot and observed every A body in the 9 Northern California Pick n Pull yards. Even after finishing that project I continued working on A body cars, buying cheap, fixing and selling. I've got some for free, others I have overpaid. I dont claim to be the foremost expert, but I have seen enough of these cars to form a fair assessment. The latest car I owned with 9" drums was a 76 Dart 2 door. I dont remember the exact build date. Its possible that at some point, one of the previous owners pulled the bigger brakes from the car IF IT ORIGINALLY had them, then swapped in the smaller setup just to make the car a roller, but I'll never know. It all was dingy and caked with grease to the point that it looked original.