k-member repair
Hole location and position is very critical for alignment. I never welded a K-member that was damaged like this. I tossed them on the junk pile. there was a reason it cracked and was it in the right position when it was welded.
Don't trust the guy that sold it to you telling you its OK. He would need to return your cash if he said it wasn't. Looks like it was welded while it was in the car. probably not in the correct position.
Why was it covered with under coat? probably hoped you wouldn't see it.