Upper control arms are not "tapped" so to speak, so what your thinking of a conventional tap isn't used.
Threads on a ball joint are "self cutting" into the metal of the control arm.
If you ever have seen a brand spanking new control arm, from any of the Mopar body style cars, there are no threads in them.
The ball joint itself cuts the threads in the arm.
Now in your case, start the replacement ball joint into the boogered up threads as straight as can be, tighten it down, and if it doesn't tighten down great, you just tack weld it to the UCA in three or four spots, around the joint.
A repair like that has been done forever.
The ball joint ain't going anywhere after the tack weld job.
You are using the correct size upper ball joint socket, or using a pipe wrench, or something, in the removal, and replacement, of the ball joint?
FYI
If you get another used arm, your most likely going to be in the same situation, in removing the ball joint from that arm, and then installing a new one in that arm.
So pick your poison, in which way to want to tackle your present problem.
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