65 Commando stock brake set up

"Commando" is an engine designation, not a car model. I presume you have a Valiant? I am not an expert on narrow body As, but I would agree that V8 cars would probably have 10" drums — I know they did in 1967, at least. Do you know that this was originally a V8 car? What does the data plate show?
Commando, meaning 273 V8 four barrel. Yes all original V8 car. Data plate, vin, and engine casting numbers show this. I think I'm going to switch it back to 10 inch drums and buy new shoes. Who knows what happened over nearly 60 years. Just trying to understand these brakes. I did see an old video online of a guy doing rear brakes on a slant 6 1965 barracuda. Didn't get great looks but I don't think his car had these missing internal parts either.