Positive. All drum/drum A-bodies were 5x4" right up until '76 when the front disks became mandatory. Only /6 cars came with front drums after '73, and there were several option packages that added disks.
But, if it was a /6 drum/drum car, it was 5x4". It's right in the factory TSB. The link has the full size image if the picture is too small to read, the TSB is on Hamtramk-Historical.
https://www.hamtramck-historical.com/images/TSBs/1973/05-03-73C page1.jpg
View attachment 1715943458
