Anything from 63 or earlier would have the wrap around windshield. Since it doesn't, then it's a 64, 65, or 66 cab. The cab might have 2 little holes at the top of the firewall for the tubing for windshield wiper fluid. See photo of my 66. I think that was only available in 66.
A 62 frame has a "V" reinforcement under the bed - see photo.
