Not sure which. I had a chance years ago (OK decades ago now ) to buy an original 65 fastback. It was all original with only 35k on it. But I needed a daily driver and it was coming up on winter in Vermont.
It’s a ‘65. Look at the chrome scallop just ahead of the rear wheels. The 1964-1/2 models had no chrome scallop. The 1966 models had a different ornament - with three toward-facing prongs. At least if they’re stock.