I had a 54 Studebaker truck that I built into a 4x4 by replacing the frame with one out of a one-ton Chevy 4x4 (and putting a 500 caddy motor in it)... I got no end of grief from the Studebaker preservationists (yes funny man, there are at least 2 if not 3 people who have that affliction) until I pointed out how I fixed the cab corners. The corners were these radius stampings that were designed to keep water in them - thus, they rusted out and since they were a tight, compound curve were nearly impossible to reproduce. Nearly (now, actually, someone makes replacements) the way I fixed the corners (and got the others off my back) was to use fiberglass matt infused with POR 15. the stuff adheres quite well to rusted metal and is like a rock when dried, will only fall off when the metal above it rots away, and makes a darn nice sculpted corner.