I'm surprised I didn't see this thread before. I am a major Mustang fan and before I got my "luxury mustang" (Lincoln Mark VII LSC) I used to own a 67 Mustang GT.

The bezel your showing here is for a 67/68 and won't fit his car.
The 64.5-66 models had the radio up higher and mounted in the actual metal of the dash, not in a bezel that then itself mounted to the dash. It was more like the cars from the 50's.

They do make a custom patch panel for modern DIN radio that can be sectioned into the dash. It's a little bit of work but it will look like it belongs there though.