flintriver,
Zeke has got it right. Here is an extract from a technical article on Jim Carter's website (it is not easy to give a direct link):
"Suburban/Panel Truck Body Rust Repairs
Replacing major rust-out between the rear fender and door of the 1947-55 Suburban or panel truck can be easier than you think. The curvature in this area is the same shape as the adjacent door.
Therefore, locate a 1947-55 donor door of limited value due to butchered radio speaker holes or a badly rusted bottom. Remove the outer panel. It has the correct metal gauge and round shape as the Suburban and panel truck body."
Other difficult spots on a panel/suburban are behind the rear wheels and the rear sill.
Good luick,
Tim
