Steve,
Your analogy to birth certificates is one I have used too. I consider the cowl tag as part of the birth certificate of the car, NOT intended to be altered.
One may be born Richard Wadd, so he can change his hair color, eye color, weight, height, hose, chin, belly and butt cosmetically. But even if he changes his birth certificate, he's really still just a Dick Wadd.
Verne