I have a 1967 coupe barracuda with a low serial number and shipped march 1966.

Did they build a Barracuda coupe in 66? The OP is the unsure and unable to confirm any part of this(Richard Petty) 67 A-body blue car. Just sayin -----without photos it can't be ---------
Oh very well could be. Back then the design teams were a few years ahead of production. They had to be. It could be a prototype or a pilot car. This is pretty early in the conversation and we haven't seen a vin tag or a fender tag yet.