I have a 1967 coupe barracuda with a low serial number and shipped march 1966.
Here is my take on this and I could be completely off.
IF Petty was to have built a 67 Barracuda it most likely would have been a Fastback, nothing against the Coupe.
IF Chrysler was behind it the car would have been a Body-In-White with no VIN assigned.
There is nothing in the VIN, the Data Plate or the body stamping that says this is anything but a normal Barracuda and quite late at that (not even close to being early, pilot, blaa, blaa blaa).
So I hope you didn't spend for a car more than you could see, one of 12,000 1967 Barracuda 273-2 Automatic Coupes.
Research the Petty Connection because nothing about the car matches the story.
Alan