B-bodies are my first love. My Duster is a 10 sec index drag car. My Cuda is a Pro Street project. The GTX? Totally street. Near stock build. With stock exhaust. (I'm guessing 400+ HP.)
I have a 2014 Cadillac XTS VSport. Twin turbo rated at 410 HP. With a friend driving it did pull ahead against the GTX. (This was predicted with its 7 speed transmission.) But not for long. The 440 was PISSED! And easily caught the Cad by 1/2 mile. No contest after that. Give the GTX that much gear? That stock 440 car would turn in high 12s. Just takes too long for the 440 to get into its power band with current 4-speed and gear set.