If it had a 9" drum, it may have got SBJ. They are not common, but, they are out there. I've seen some 73 cars with SBJ 9", never anything later. One friend in Colorado has the car mentioned in my post. If it's been swapped, they did both sides and everything... He says it looked like it left the factory that way.
Crazy deal, the databooks show only 10" drums up front after 1973.