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

Not trying to turn ball joint around. Keeping mounting surface towards the spindle it will only fit the correct side. The recess on mounting surface inhibits swapping to opposite side.

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That's my point- you don't swap them to the opposite side. Only the spindle gets swapped side-to-side, not the ball joint. The recesses stay towards the center of the car and receive the bolts as normal- you just are bolting them to the swapped spindle.
I've done this many times, there is no issue.