Help ID Lower Core Support

Car is a 74 Dart Sport 360, and while I knew my lower rad core support was beat up and modified at one time, I am starting to wonder if it's from another car altogether. I have a new support from US Car Tool, but want to fix anything that needs fixin before I weld the new piece in.

I've looked at pictures of factory replacements and they definitely don't look like what I have.

Any help with identifying and/or recommendations on what to do (if anything) would be greatly appreciated.

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