There is some product (help me out David) which is essentially fiberglass that you can use to cover up rust damage (after removing the rust). It hardens pretty good from what I've heard.
2007 Premium MustangCoupe (V6).. Please don't shun me
Replace Full floor pan
Replace Full cowl
Replace Radiator support
Shelby Drop done
Front disc brakes on
4 wheel drum to disc conversion, rebuild front suspension/steering, taillight panel, trunk floor,302 and AOD upgrade, wiring harnesses back in, and hopefully only patch panels on the quarters