Rod
Sign does say that as does a lot of other info on Beechey etc over the years.
First Mustangs were built in March 1964 and are referred to as 64 1/2 and Ford called them 65's.
USA used to/still does release the next years model mid the previous year.
Its a very early K code built Aug 3rd 64 in San Jose and was P = Prairie Bronze and had drum brakes all round ex factory , the fronts Beechey replaced with discs after 1 or 2 meetings.
This sign was on it at MCM at Eastern Crk a few years ago.