A Challenger puts forth a challenge, and in the concept of muscle cars it would be a head to head (combat) such as a race down the 1/4 mile track. But that would be dificult to incorpoeate into a logo of small proportion. But how about the knight in shining armor with his jousting pole ready for the fight, but I'd leave out his steed, don't want to associate with the mushtang croud. Or instead of a jousting pole he could just be holding a massive sword.............?