I know, I'm nit picking, but, just to clarify....In 1973, you could get 9", 10" and disc brakes. The 9" brakes in 1973 were unique. Starting in the '74 model year, the 9" brakes were discontinued. After that it was either 10" drum or disc. All the '73-6 A-bodies with drums have the small bolt pattern. All the '73-6 A-bodies with disc brakes have the large bolt pattern. The '73-6 A-body upper control arms were all the same regardless of which brakes it came with. There always seems to be a bit of confusion about that.