I made a small patch (about 3/4″ x 3″) and brazed it into place on the metal header, where it had once upon a time gotten damaged. Then I primed the header with epoxy primer.
I noticed that the hole in the wood header for the windshield wiper shaft does not line up very well with the hole in the metal header. I will have to fill the hole and drill a new one about 1/8″ to one side.