Rust investigation.
Back when our cars were made (ours meaning ALL of the A bodies owned by everyone here) they didnt put as much effort into protecting the body/chasis from corsion thru fully coating the ENTIRE body with all the chemical treatments and acid baths, etc. that they do to todays vehicles. Exposed bare steel, even kept bone dry, WILL corode eventually because corrosion is caused by oxygen for the most part. I delved into this slightly in my response to another thread on this section of the forum, the post titled "Rust Converter/Encapsulator".
The only way to slow the development of corrosion (aside from making sure all seals and gaskets are intact and working as intended) would be to give your car the same treatment they do to new vehicles: strip it to bare chasis then have the whole thing, along with all the individual steel pieces, submerged in an acid bath then all the corrosion preventative chemical baths, then dip in the coatings baths. Very dificult to do, could be done if you really really wanted to. I don't know many with that much ambition though. Next best thing is, if you take it apart to do any repairs, treat everything that you can get at with a rust encapsulator (dipping is still best if at all possible) and coating with the best primers and paints available. If it's exposed to oxygen, it will corrode.
Then again, there would be one other way I can think of that would stop rust and dry rot almost completely. Build a big hermeticly sealed glass case to put your car in, then draw it to a vacume and fill with dry nitrogen. That should curtail corrosion for at least the next couple hundred years. LOL.
Amazing isn't, that which gives us life is so very harmful to everything else on the planet.