How many times has a parts car become a builder

Depends on your perspective of what is saveable- I've gotten two "parts cars" that were better than the original project car, and the roles became reversed. They came from further south than here in Wisconsin, but it can be amazing the difference even a couple hundred miles can make. A few patches versus a year's worth of bodywork (at my speed) wins out every time.
I think an appropriate question is "Why do some people call a car junk because of some minor flaws, and the next guy thinks his rusted out pile of trash is worth a fortune?" One of the great mysteries of life.