We've FAILED cars on PPI reviews from "reputable" dealers on more than one occasion. The typical answer is, "well, I am an honest business man but not a mechanical expert on the GT and I was told by the person that I purchased car from that.... and the carfax says, ...."
If a reputable dealer says that he is an EXPERT in Ford GTs and/or has EXPERT staff on hand and they say that they have done an inspection and the car has passed with flying colors, then that's one thing. You are trusting a man's word. But if a seller (non-expert) says, "yeah, this car LOOKS real good and the guy I bought it from seemed real honest, blah, blah blah...."
Caveat emptor.