9" vs 10" drum brake spindle question

Ok gents I’m hoping to help a bit here.
A body front suspensions used two different part numbers for lower ball joints from 64-72. One was for drum the other was disc. Difference was the drum balljoint has a 1/2 hole while the disc has a 9/16 hole. Otherwise they are the same casting. If you have a 9 inch system you can swap only the spindles to use 10 inch spindles.
Leed and SSBC both use a mustang rotor Raybestos 6004R Centric 121-61053. The only difference is if you order the A body kit from SSBC they have the dual pattern drilled rotor. But if you only want to use BBP you can buy mustang replacements. And SSBC is still very much in business and providing parts. I question their method for rear seal because they use the larger mustang seal.
Now on to the 73 and up. For 73 model year all A bodies started using the B body style lower ball joint. Moog PNs K781 and K783. They also started using the B body upper balljoint K772. To use the single piston brakes you have to swap upper control arms or use the balljoint adaptor. The 73 and up is the basis for everything that’s offered with a single piston caliper.
So now that I’ve buried everyone in tech details, I hope the clarification makes decisions easier.