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

While we're on paint-

"light blue poly" is not "Petty blue"

Actually called "corporate blue"/"true blue".

Petty blue would have been a special order color in 67 (and 68).

IIRC it became an optional "HIP" color in 1970.

In 69 the code would have been "999" for special order.

I believe this applies to 68 as well, not sure for 67.