There were a few stubborn pricks on Moparts that swore that there were no drum brake A body cars built for 1976. One dipshit based his claims on parts books that didn't list front drum parts for the year. A few members chimed in with posts about drum brake cars they had only to be met with claims that their cars must have been swapped TO front drums by a previous owner.
With car stuff, I try to make sure that I am right before I make absolute statements. I'm still not 100% on this. Maybe there was no Federal mandate but was there an internal Chrysler decision? The AI search I did showed the last 4 wheel drum vehicle was a 1980 Jeep CJ 5. Not everyone jumped on the front disc bandwagon right away.