I have seen a 2002 WS6 N/A full bolt on with 4.11 gear make 386 ft/lbs and 430hp RWHP without even opening up the motor. The 450 to the rear wheel is most likely a real number. The 540-550HP to the crank is made up. But i agree, if you plan on hooking up in the slightest, BOOM goes the diff. Will definitly need to upgrade to an 8.5-9" to put that power down.