Buying from a very reputable dealer would help, but I suppose they could be fooled too. I would think some one like Shelby would be able to know a cars complete history if you were buying from him. With the aging of the cars, a PPI becomes more and more important. My dealer was great to deal with, but I bought mine a year ago with low miles and was guaranteed a no stories car. I had it all in writing, and again, dealer reputation is paramount. Best of luck with your search.
Rick
Rick