It was my understanding that the '71 and earlier high compression 340s came from the factory painted orange. The de-tuned '72 and up 340s came painted blue.
I'm 64 and grew up and lived on the Canadian border (Calais, Maine).
We drag raced all the time on late weekend evenings during the summer on a straight stretch about 20 miles out of town. I had a '73 340 Duster with the "blue" motor.
I matched up on many ocassions against a Canadian '72 Demon that belong to a friend of mine. He swore it was stock and I had no reason to doubt him. I could never beat him, but I can distinctly remember the 340 motor in his car being orange in color. Was it the high comopression 340 engine in a '72 Canadian car? Obviously, I have no way to prove it to be, but it was consistantly faster than my '73 car. We even swapped cars on one occassion and I beat my own car with his...LOL Maybe he just had a steeper rear end ratio. But I know for sure it was an orange motor in his car.