replacing upper control arm

Lot's of people just tack weld the ball joint in a couple of places when the threads get boogered up, in the replacment of the ball joint.
Or just find another pair, and then install them.
What year car you working on anyway?
That will determine what UCA that you will be needing.
72 and earlier.
or
73-76
If you go the replaement route, i can help you out.
I have UCA's in stock, that i sell to members here, and thru eBay.