The story is true as I have talked to one of the characters about the car and can recall some of the details of other aspects of the story. I even had one of the programs pictured in the story at one time. Is it "the" car, probably. But, it is tough to prove it outside of paint chips and stories since documentation on many race cars modified to this degree is never easy.
It's nostalgia and it worth whatever that nostalgia is worth to someone, much like any other car of its heritage and era. Heck, even Petty has acknowledged that they never cared much about last years race cars, which is why they have a fair amount of value today. Will it sell for more than $10k, probably not now, but it may someday.