‘67 Disc/Drum - upgrading rear axles to 5x4.5 - any replacement drums?

9" drums on what? Not an 8.75 rear.
Are the new axles set up with small or large center register?
Small would be the same as your original A body 8.75 axles...if that's what you have.
Did you order the axles to be used with your existing brakes?