C-pillar question

jos51700 said
My '72 Dart originally had body putty in the roof-quarter seam. The vinyl top eventually rotted and the body putty has become microplastics.

I would prefer to fill it with lead for longevity, like older Mopars, but I'm wondering; does anyone ever make a sheetmetal patch that get fully welded over this joint, so that the filler is just more of a skim coat instead of a massive slug of filler?

I figure the patch would have to be hand-cut for each side, but could be perimeter welded using small welds until its sealed. I'm figuring you'd want weld-through primer first to prevent rust from the inside. Or is this a terrible idea?

I have seen people use metal as you mentioned, and it worked out just fine.

Don’t know if this will give you another option or not, but I had that same problem.
I wire wheeled the filler out.rough sanded the area and used short strand fiberglass. (by Bondo)
Been on there for 5-6 years and still looks like the day it was done.