That's kind of along the same lines I was thinking... First off you need to give readers the entire story so that they can make up their minds whether or not you have a case. Just not enough facts in your original post to give a clear picture of all that transpired. I would question why a "new" Challenger had no Catalytic Converters on it to begin with as like you correctly pointed out, they could not legally sell the vehicle as a new car without they....so why would they remove them in the first place? Is the car a trade-in, or perhaps a salesman's ride that was mod'ed for some reason?
Sorry, but if you are looking for support, you need to give us the "entire" story, not just half of the story......
(There's a lot more to this story than you are giving us)
Let's be fair to the dealers, and not post "half" stories.........