I'm not sure what you're remembering, but, all drum/drum A-bodies were SBP. In '73 the 10" front drums went from 10x2.25" to 10x2.5", but remained SBP. And the 9" front drums went away. That corresponds with the switch to large ball joints. But the drum/drum A's were all SBP from the factory.
And you have to be careful with the online listings, because the rear LBP drums are also 10x2.5" and those online listings screw up front/rear drum listings all the time.
Just measure the bolt pattern. You should have the 5x4" pattern, with a 10x2.5" front drum.
View attachment 1716145717
If you have a 5x4.5" pattern, someone has swapped your spindles out for B-body units and you'll have to use B-body parts.
FYI, the drum hubs are NOT reproduced. You will have to find used 10" drum hubs.