Until Andy chimes in, here is what I know.
Frame, outriggers holding the trunk, and the ones in front of the back wheels.
<span style="color: #000099">Those outriggers named are often the first to go, notably the "ones in front of the back wheels"; they hold the radius rods for the rear suspension. Rust there makes for "interesting" handling!</span> :shocked:
Floor pans, driver and passenger
In the trunk right after the spear tire well were the metal is bent up and then flat again.
Spear tire well
<span style="color: #000099">All of the above aren't necessarily as critical from a structural standpoint, and they often occur from the inside out (years of damp carpeting, etc.). But they do add up to big problems once they get bad.</span>
Rocker panel
<span style="color: #000099">The part you see on the outside simply bolts on, so rust there isn't a big deal. However, the "sill" itself can also rot away and cause problems.</span>
The metal along the rear bumper between the trunk and bumper, outside
Front inside bumper near the ends
Front wheel well were it joins the front end
<span style="color: #000099">These areas again are mostly cosmetic. The front and rear valences bolt on and can be replaced. Behind the front valence, though, is a crosstube that is part of the chassis and supports the valence and the bonnet hinges. Patch panels are also available to repair rust on the bonnet itself.</span>