Got the formula
I'm not sure about how much you lose from the clutch to the wheels, but I would definately be interested in just how much is lost, also how much from an auto.....but in answer to your question, this link should work, if not, just go to the tech archives and look on the second page for this. Combo 6 I think is 430 hp, I think the next one is 450 hp, I'm sure others can help you more though...
http://www.forabodiesonly.com/mopar/showthread.php?t=1175