That is one of the most rusted GT's I have seen for a while. I know the car has sentimental value, otherwise I would suggest you invest your time in a better base car. If you are interested in a photo essay of a GT restoration that was in similar condition and turned out AMAZING, have a look at http://home.tiscali.be/rudolphnevi/Opel-GT/index.htm . Rudy did a terrific restoration and his site has some excellent photos of the process. Good luck, and happy welding.