Ted,
I have the ECS system on our challenger and the B body mufflers on the way for my charger. Why? Because I want my cars correct like they would have left the factory. And yes, we drive the crap out of our cars but also get a lot of maintenance with polishing and cleaning them before any big show or after a long drive on an AACA tour. Why go through replicating all the small details like tags, inspection marks, etc. only to settle for an inaccurate part. Again, there are MANY different levels of restoration that one could do with their car. Cosmetic only for a nice cruise night car, another would be where you clean up the undercarriage and maintain how clean it is and undercoat it. Then you have the super high end cars which pretty much are OE standards that have to have every nut and bolt correct with correct markings and such. Our cars are not the cruise night car although we do go to an occasional one for fun but our cars fall mostly in between the other two classes.