Keep in mind that the instrument cluster bezel for a std. '65 GT car is exactly the same as the deluxe interior piece. Some think that the std. is actually molded in camera case, but for '65, there were black camera case stick-on inserts. So, the shell is exactly the same, just different inserts.
The gray warranty plate is of no significance as it was normally used during that time in production.
Do you have any original documentation like a window sticker or invoice that shows how the car was ordered/sold? Without something like this, there really is no way to prove that the rally-pac was factory installed or if the dealer installed the wood grain dash parts. Keep in mind that even if they were installed when the car was 5 years old, that was about 43 years ago. It wouldn't be unreasonable for someone with a steady hand and attention to detail couldn't have swapped out the bezel and for it to appear as original all these years later.