Mojoecool81,
some other key areas to look are:
1. is the underside of the trunk nice and smooth, it should look like metal not the typical hand laid fiberglass (I put a pic of the trunk).
2. the tail light wiring should have the correct part #, look on the passenger side of the trunk where the wiring connects with the T-bird lights. There should be a purple tag (it may have fadded clear) with the part # C8ZX-14405-A
3. The grille should be a 67 grill and even though your car should have Lucas lights, the grille mounting brackets should still be there, I included a pic of the brackets in the grille).
These along with things xcodegtcs talked about are key, but the only real way to determine the authenticity of the car is through Marti auto Works. I would recommend spending the money because if you have proof in hand, it will make the value much more than a clone or just a regular 68 coupe.
Please list the car here first to give those that have a passion for this car can have the opportunity to buy it first. Thanks & good luck.
PS do you have any pictures of the car?
Doug