1. It was THE FIRST muscle car, bar none.
2. My college roommate bought one brand new in 1964 (2dr post sedan, 4-speed) and it was faster than $#!T
3. I cannot afford a 64 GTO now (I do remember when you could have bought a good one for $2K), but I did buy a 1964 Beaumont (yah, not a 389, a Canadian-built with a weeny 283, but it still looooooooooooks nice) so another reason to go with 64.
4. See #1.