The truck in my signature gets about 9mpg (loaded or empty) in the city, and i've gotten as high as 16mpg (empty, except for two people and two full gas tanks) with it on the highway. My average mpg on the highway @70mph has been app. 13-14mpg (loaded or empty). many folks say that's pretty good for a 454, but take into consideration that this truck runs like a clock, is always kept in excellent tune and I don't have a heavy throttle foot. 454's may be a bit hard on fuel, but DAMN you can't beat that torque!!
For a truck, it's far better to have that torque and not need it, than it is to need it and not have it.