[HugoBear]

I would tend to agree with Rick. I don't believe there is legal recourse unless you can prove that the seller intentionally misled you and not even sure if that would even matter.
When I bought my 87 from a dealer, there were several things that popped up that did not show up in the PPI.
That being said, the seller never specifically said that there was not an issue and then there was that specific issue like the rust.
For a 48 year old car and a model of car that is known to rust, I think you will be in a tough spot.
All of this could be a non issue if the seller did not know of the problems and is willing to take it back but I don't think he is legally obligated to do so.
That is what scares me about these care. I don't know enough about them. I'm sure even expert flippers get into cars that are not what they thought they were.
I think what folks need to understand is that even if this guy doesn't take the car back, it doesn't necessarily mean he is "bad guy." if I were a seller, I would be he could have bought this car for market price and got something he didn't expect either.
I truly hope it works out for you and the seller. Good luck.