I had two of September built '72 models. Both were 9" front drum with the large ball joint. The spindle is the same one as the 10" drum brake, so, they both use the A2 and A17 bearings. If you look in the factory and aftermarket parts books, only one control arm, spindle, and ball joint is listed for a '73-up A-body model. I don't know what to say on the one you had. Maybe it had been changed for some reason? I know those early 9" hub and drums were a tough on to find, so, maybe they reverted back to something that would bolt on. Strange things can happen over these last 50-60 years.