I'm sure he's right about the '71-'73 and '74-76 bodys being from different tools Tom. Just compare them and you'll easily see there's way too many differences not only in tooling marks on the inside but stuff on the outside. Wheel opening shapes, windshield trim, *PIC*
character lines down the side of the car, rear marker lights, just to name some off the top of my head. Things that there would be no reason to change as they did not change on the 1/1 cars.
I'm not saying that the whole kit is different, just the body.