You're correct about the 66 dash and rear sheet metal, which makes me wonder why it would have a 65 VIN. Even if someone replaced the entire front clip, the VIN is attached to the door frame so it ought to have stayed original. The fender tag might be from either one, depending on whether the inner fenders were replaced-- I don't even know if it's possible to hang 65 fenders on 66 inner supports. I do know that the entire hood leading edge shape is different.