[Stefano]

While this may not necessarily be statistically correct I have found that most of the Muscle cars which I inspect (that would be more than half) of all makes and models are proported to have their original drivetrains but less than half actually do.

These are regular, everyday, mass produced (usually in multiples of 10,000) muscle cars like GTOs , SS 396 Chevelles and Super Sport Camaros.

Super Car drive trains were less likely to Survive, just as T Billigen stated. Many of the Super Cars were full blown race cars if not at least weekend warriors, or steet racers.

The temptation to take any solid lifter muscle car with a free breathing exhaust well past redline can be irresistable.

One split second and missed shift later you may no longer have an original motor.

I would say that less than 25% of the Documented and found Super Cars have the engine, trans and rear axle housing that they had when they left the dealership as new.