Don't rely on the door for determining what kind of car it is. All it'd take is for the drivers door to have been replaced and repainted. The real way is to look at the dash VIN to determine if it's a mach.
No C6
AFAIK on the small block cars, as stated before.
I don't believe the rear axle had VIN stampings and only some of the engines/trans got the stampings. Date codes may be your best bet in determining if the motor is original or "correct"
