that much rust on the quarter,dropdowns, etc....probably tip of iceberg. Been there done that. If full quarters are available then you at least have the option to get in there and really see what's eaten up. Most of our cars that were allowed to get like that were driven in the rain and salted roads with all those holes present rusting areas that you'd never thought moisture could get to. If you're like most of us...once you know the rust is there you'll never forget it if you just cover it up with POR 15
.....Good luck.