I would agree with 66submarine. Keep this in mind though: Add a '63 to your 64-66 list.
'63's are unique in that they have the wrap-around windshield but they have the coil spring front suspension. They also have the older x-frame.
In 1963, along with changing the front suspension from torsion bars, to A-arms & coils, the frame changed from X-frame, to ladder-frame, as found on the '64-'66 truck.
