It was a common practice for the guys with cars pre- 1940's, Back then the roof was an insert of cloth and wire and sometimes tarred or doped to stop the rain from coming in. So they would go to the wrecking yard and find a car with a good roof section and remove it to weld into their car. Some guys liked a corrugated roof as it provided stiffness and strength. You'll need some welding tools and grinders, vise grips etc. etc. also a plan of how you want to cut away the bad parts of the original roof and how to fit the new section in. Leave it a bit larger in all dimensions to give yourself some working material. Take your time and weld in short burst to minimize warpage... OH, and share some pics! rofl....