Rust quickly reminds us that these are 55+year old cars and this is to be expected.
My 68 valiant has a similar problem but for me it's the torsion bar cross member. I intend to change it out but life has been preventing good progress. I also didn't notice it at first till I got under the car to do some other maintenance. I also did not blame the seller because the problem started long before either one of us were around.
On my car its very strange, Arizona car and this is the only rust on the whole car.
Chin up and fight the rust.
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