It is a '66. It was wrecked when it was new. There were basically not parts available except for '64 1/2 wrecking yard stuff and it was sectioned in the RT rear the old fashioned way.
Then years later, it was hit down the RT side and the front half of the RT qtr was sectioned. Again - '64 1/2 parts used but those are the same as the '66.
I was given a Chinese qtr to put on it. That was no fun at all!