Ball joint fit in upper control arm

Last night I put new upper ball joints in my 67 cuda. One side tightened up real good and the other did not, it feels like it is stripping. It was not real tight in the first place, unscrewed without a lot of effort.

Should I replace the uca or can I tackweld the balljoint in? Another used uca may or may not have the same problem, so you're gambling on getting a good one.

I'm open to suggestions or solutions.

Thanks, Gary