oh yes they did. My Dad had a 76 Feather duster, had 9" drum brakes all the way around. and 4" bolt pattern. manual brakes to boot, no power booster. /6, 3 speed on the floor, manual steering even.
I have (had?) a book of all the TSBs for 1976 and if I'm remembering right there was something about front disc being mandatory after 1/1/76, by law... but the early production 76s could (and some still were!) 4 wheel drum equipped up until then. There was a service bulletin that spelled out all of that info... .
I remember that car quite well as Dad bought it when I was 13, as a "work car" for a few years til I got my license, was supposed to be my 1st car. My brother wrecked his 74 Charger and needed a car "like yesterday" at that point to get to work so he got it instead. Im still pissed.... Guess who had to do all the work on it while my brother owned that car?? Yup. ME.