Hi John,
Over the years many folks have modified wide window cabs and put a cameo bed…and called it a cameo. One of the unique aspects of the cameo was the back-up lights. And one of the ways I've been able to check real authenticity is to see if the back-up light switch is still attached. There is a very hard to find bracket that holds the very hard to find back up light switch…these both are attached to the steering column.
If you have these, these's a good chance it is an original cameo.