I'd be curious to see the list of "classes" you had to choose from.
Clubs putting on small shows are often stuck combining classes. They often change from meet to meet as they look to see who all is showing up at their shows. The more late model cars showing up, means the more classes in those. My local clubs often have a "Mustang Pre 1978" class and then a few classes covering the later Mustangs. I don't blame them as they might, MIGHT have 7 pre 73 Mustangs show up (and we are a Mustang club), then they will have 20 from 2000 to date.
So was there a "Shelby" class? Or some "Modified" which meant your Shelby and Cobra II wound up in the same class, along with modified cars. Perhaps they had a "Hot Rod" class also. It's always a Cr*P shoot on where to put your car. My friend with a heavily modified 1970 Mach, looks for the class that is "modified" or "hot rod" or "Performance Car" classes. I decided long ago, to just put mine into the closest "Mustang" class I could and enjoy being out and not worry about any trophy. Which are up in the attic anyway. Or as stated, drive over, put it in "Display" and leave 20 minutes before they even begin any awards.