65 GTO vs. Clone

Am starting to consider purcashing a 1965 GTO or possible a clone. Is there a definate way to establish whether the car is the real thing or not. I'm sure PHS registration is the best way but are there any less known or less changed ways to determine real or not. Thank you.

check the inside of the rear quarter panels to seee if it has several holes filled in where the lemans letters were about the same area as the gto badges
hope this helps

the old saying that the 5n on the trim tab goes for those care built only in lansing or kansas, this is a good way to help support the fact!