If someone takes the time, energy, and money to get an old Plymouth back on the road then I see no reason for them to be ostracized from the POC. If your car is a daily (or frequent) driver, some modifications help the car be safer in modern trafffic. It isn't economically feasible to bring some cars 'back from the dead' if 100% originality is the goal, so modifications are good because at least that's one more Plymouth that survives. Personally, I'm not in favor of massive modifications to a nice car (Troy Trepanian comes to mind) but that's another story.
A real POCO is a very good idea. If it is launched officially, I'll join.