Keep in mind that most of the common rust areas on our trucks start rotting from the inside-out. :( A simple grind-n-spray will probably not stop anything, only delay the inevitable. But then, a weld in patch won't solve anything if you don't have access to the backside to properly clean/paint it (rockers, frame etc). It's a tough choice for some of us as to how much effort we really want to throw at it. :(
If your floors are rotting, you'll want to find/seal the cab leak that has been letting in the water.
Bottom line, I hate road salt. :fs1: