Is this crate 6.4 an assembly line SRT8 6.4 or something else? An assembly line 6.4 with a tall mopar intake, dialed in appropriately sized carb and long tube headers can actually put out over 550 HP without ever removing the valve covers, I have heard as high as 580 with a wilson modified tall intake and the drag strip numbers seem to be able to back it up. Look what a good cold air intake, slightly bigger throttle body, true long tube headers and a good tune do to an otherwise stock 6.4 in a stock challenger or charger.