Is there any difference in the size of the brake booster in a SE and a 12A car?

 

All I can tell you is if it has dums in the rear then it is the smaller booster and If it's a disc/disc set up the booster is like an inch bigger. also disc/drum setups usually need residual pressure for the rear and also have a different proportioning than rear disc. Either way If you have discs in the rear make sure you have the right propotioning block. The size of the booster will just determine how hard you have to push.