What Gary just described is a Concours d'Elegance type show. Sure, in shows like that everything has to be stock and correct for each vehicle. Very few car shows are judged at that level, especially those who allow PT Cruisers. If my Cruiser was judged on "stock" parts, I'd never win anything. lol
The types of car shows that rocketsigntist is interested in don't go to that extreme. Rocketsigntist, if you're interested in showing your PT Cruiser at some local shows, just try it out. As I said before, it's more about the people than winning. Go to meet some people and have fun looking at all the rides that others show.