Showed it to a couple of body shops and everyone is basically recommending replacing the rear quarter panels at this point. Assuming I can even find new quarter panels the labor and other consumables and paint is going to be expensive.
I am starting to look into more creative ideas of taking care of these rusty areas in the rear quarter panels. Here are two that I have had suggested to me, both seems equally awful. Basic idea is to use a wire wheel to take as much rust off as I can and then douse it with Rust Reformer to stop further spread. And then
1) Either cut out some sheet metal and JB Weld it on,
2) Or, seal the open section with FlexSeal tape and fill it with expanding foam.
The offending areas are hidden behind the bumper so they don't have to look pretty.
View attachment 2438426