Beautiful ride no doubt, and having so much original parts and such makes it that much more special.
Have you tried clay to remove some of the embedded rust on the side? I can't tell from the pic but it could be one of two real things:
#1. Body work underneath going bad. I doubt that's the case as you'd get ugly bubbling and such under the paint.
#2. Either rail-dust or brake dust particles (tiny metallic pieces) that were embedded into the paint. White shows contamination worse than any other color. The good news is that this may be fixable. I believe these 'Stangs were single stage enamel paint, and once clayed, you'll see a big increase in the brightness and intensity of the paint. Of course machine polishing could potentially bring the paint to a like-new condition, but is a lot more risky than claying.
Regardless, good luck with the future sell and no doubt it should fetch a pretty penny: She's a beautiful car and a fine piece of auto history. I wish I had money to buy it! :thumbsup: