Kelsey Hayes 4 piston Disc brakes

ir3333 said
Can you use 10" drum brake ball joints on 4 piston Kelsey Hayes Disc brake spindles?
..do you drill the spindles to 9/16"?

You are asking about Lower ball joints, arent you?
You drill out the mounting bolt holes of the ball joint to 9/16 inch, not the spindle.