Re: 1966 Mustang in Adelaide 1966.
I'm sorry, I was a bit of an ass this morning, I shouldn't read the Pontiac Forums before this one... I'd see if Watkins Chrysler is still in business, if not, if any of the family members have records. I don't know what the record keeping was like down under in the 60's, but they weren't that great in the US. However, generally things such as cars that were used in promotions, particularly ones that really weren't intended to sell, often had a little more trackability than your typical "on the lot" car.
I'm only about 2 years older than you, and the only car I remember from 1966 was Miss Harding's blue 'Vette. and in 1rst grade, I recognized the hotness of her and the car. Good luck, and again, I apologize.
Chewing on asphalt and drinking dinosaur wine