All you have to do is pull apart a lapped weld that looks perfectly clean to see it is RUSTED inside and you will understand.
![Big Grin](http://67-72chevytrucks.com/vboard/images/smilies/biggrin.gif)
But the thing is, the ENTIRE cab is made of them, so one more isn't a big deal. Just be sure you clean that stuff up good, epoxy primer it, and seal it with a good seam sealer.
Brian