I knew this was true of '66s, but just ran a google-image check to see if it applied to '65s, too, and it does: The Mustang fastbacks, whether GT or "base" 2+2, did not have the fake vent trim at the rear of side coves. (That was a pain to sand out of the coupe donor body when I built mine.)
Also: The GTs didn't have the chrome rocker trim, but the base cars did. I left them on my conversion just to be different (and as a non-GT), as the original '66 annual fastback was definitely a GT and didn't have them.
Just thought you'd want to know. Nice resin body, BTW.