I know nothing about body work, except what I've read. But I'm an electrician from the days we soldered and taped knob and tube. Your plumbing solder and ours was different even then. Go check the Eastwood site. There's new solder products and tools for automotive work, and you probably have the skill to use them. Different fluxes, etc, also. It's still considered the high art form in custom work, for guys who can do it themselves, or afford to pay more than scale.