Those panels could be easily restored with hot spray zinc metalizing ( think of a combination of a mig-welder & a spray can) it would fill the missing areas & holes with solid metal (unlike lead which is soft) this method has been used successfully on rotted out panels on collectable cars.
there's a shop here locally who does it, along with media blasting ( plastic & glass-bead & soda blasting) the hot spray zinc metalizing will not distort or warp the metal like hot dip galvanizing or lead-work, as for durability, zinc is harder than iron.
It can be done!
Holy cow ! I've never head of this method of metal working. Definitely will have to check into this as I was told by a friend who is retired from auto body-working that the panels could get warped from high heat. So, thanks for this great informational tip.