After some of thought and catalog shopping, I've come up with the idea of using a lower door patch panel with the replacement rocker panel welded to the bottom and modified to fit the curve. If you look at the profiles of the two (the door and rocker) next to it, it has the same curve you would need to get you up about a foot up from the bottom of the rusted spot. These patch panels very from 7" to a foot and a half tall. The rocker is a good line match to the lower edge of the fender. Just cut it, bend it, weld the two together and grind'er on down. Granted I haven't tried it yet, but that is my plan for this spring. These are some examples, and I always see them on ebay. Check it out let me know if I'm crazy. I figured it's better than bondo or starting from scratch.
http://www.brotherstrucks.com/prodinfo.asp?number=ODB5900
http://www.grumpystruckparts.com/item329077.ctlg
http://www.grumpystruckparts.com/item390597.ctlg