QUESTION FOR UCA BALL JOINT SEPARATION

One more time; it matters not a hoot where the rib ends up. The only thing that matters is where the the turned out tube ends are finished to; these locate the bushings stop flange. And the next thing to be concerned about is that the bushings themselves are properly factory assembled.
So now that you have a replacement arm, and after the bushings are pressed out, measure that distance and compare the two. It may well be that the replacement arm is narrower there, the same way that it is narrower at the rib. And that would make the wide arm defective. But I think I would just have dressed the max dimension down to re-position the bushings where they need to be. Oh wait I am not in NewZealand,and I have spares. :) And now, you too have a spare!