the main spots to look for rust on an EB are the rocker panels, kick panels, and the tailgate will be the worst. I had real problems with the rear of the bed.
The frames are the best things about these monsters. Mine is 33 years old and barely has any rust!
As for the softops. They are strickly an after market product. They came factory as a wagon(full top), halfcab and the roadster (no top or doors).
Good luck with your search. It's just as easy to find a great bronco as it is to find a real pile of crap, so just look around and you will find your new obsession

Tim

email me if you need anything else

Taking pride in what most take for granted.