73 E body front disc brakes conversion on A body. Where did I mess up?

I did this for everyone. Is this what you wanted. If you look closely, the arm is not flush with spindle. Will not fit down into recess. That is passenger side ball joint on drivers side spindle.

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Okaaay, gotcha! Sorry for the confusion- it just wasn't making any sense in my head!
I have never come across that on a ball joint before, Proforged, Moog, or whatever.
What I would do is use appropriately sized machine washers (not just normal bolt washers- use machine washers) in the recess between the ball joint and the spindle.
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Should be available at good hardware stores, Fastenal, McMaster-Carr, etc.