Today, we worked on patching a couple places that looked to have some pretty serious rust. I don't know the proper name for the area, but I think of it as part of the frame of the body. The piece starts under the back seats, arcs up over the rear axle and goes all the way to the rear. The rusted part can be seen here: There is 3 layers of metal in that area. I cut through the outer layer and found the 2nd layer is a bit pitted, but when cleaned up is still in pretty good shape, and solid. Dad scared up some sheet steel and made up a patch in a couple hours, then welded it in. I think he did a great job - it would have taken me a week, and wouldn't have fit nearly as well.