Boy wish this one was closer, think its kind of a deal. https://spokane.craigslist.org/pts/d/spokane-1979-chevy-impala-wagon/7272374113.html
True... If it was a Pennsylvania car, the back bumper would've fell off cuz the supports would've rotted out behind the bumper. I never could figure out why those late 70's GM B-Bodies would do that back in my part of PA. And the bumper would rot through in the middle. Same with those late 70's Continentals - but not with the Marquis or LTD's. Must've been the design. If it were an Albuquerque car, the paint would be chalky (if it had paint at all) and it'd have 400K on it and somebody would be living in it....
Cheaper chroming process plus lack of water drains compared to other models. The bumper and sheet metal would trap moisture in them that didn't easily drain out or evaporate. I suspect that the plastic bumper fillers that the car companies started using in the mid-'70s didn't allow for air flow as well as the earlier cars that had everything molded around distinct gaps. Cheaper sheet metal too that wasn't properly treated for rust or painted in those hard to reach spots as well as the earlier cars. Lots of little things that added up to funny rust problems between a '60s car vs. a '70s or '80s car. I know GM's problems with water-based paint and base-coat\clear-coat from the late '70s through the late '90s led to all sorts of issues that just weren't present on cars before then.