Another dumb question

I am going to put '39-'48 backing plates on my '31 Ford. My dumb question is........can I still use the mechanical drums, or do I need '39-'48 drums? Thanks, and go easy on me, 'kay?

 

You'll need the matching drums...

 

model a is 11" later is 12

 

You can do better
a LOT better than Lockheed brakes
look at my posts where I show 39 Lincoln/75 Chevy wagon Bendix brakes
mine are self adjusting and use 1940 Ford brake drums