Guess this factory TSB is wrong then? Or maybe you just aren't remembering it correctly. Front 9" drums went away November 1972 for the '73 model year. I was mistaken about the rear 9" drums, those were still around for '74.
Here's the important part
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The whole bulletin, No. 05-03-73C
The 1970 Hamtramck Registry "1973 Plymouth, Chrysler & Imperial TSBs" Page
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The '73+, slant 6 cars stayed 4 wheel drum and SBP standard. Front 9" drums went away in '73, only way a '73 had 9" front drums is if it was made before November '72. After that the front drums were 10x2.5" and SBP (those cars also have large ball joint UCA's). All the '73+ V8 cars were front disk, rear drum and were BBP. The slant-6 cars could be had with 4 wheel drums (and were SBP) until January of '76, after that all of them were front disk and BBP. But there were a lot of options even on the slant-6 cars that would trigger front disks, the towing package was one, there were others. My '74 was a factory slant-6, disk brake BBP car and it had very few options.
All of which is irrelevant to this thread, because the OP's V8 '74 would have had front disks, would have been BBP, and would have had 10" (or larger?) brakes.
