Charles, Cutting out of rusted areas and rewelding in of new metal that matches what you cut out, is a perfectly acceptable process as long as the grinding and finishing of the fix is done in a way that is neat and tidy. You don't want the fix to show.
My champion120 and my 61 E had rusted areas cut out and replaced in a very professional manner. Your cost in time and money to drill spots and disassemble a complete body sub assembly to repair a small section of spot welded flange would be extravagant if you can cutout/replace. Just be sure you get it all so it doesn't pop rust out after it's painted!
