Patrick I wasn't meaning to directly compare the two, but rather show how technological advancements in engine design have brought tiny V6 engines to the door step of older V8s, thus Ford's reasoning behind killing the 5.4L and going to a brand-new engine.
AFAIK, the Boss 777 will not be production run, but rather a testbed and one-off for SVT to show off. The mileage of that engine would be terrible. I honestly believe there shouldn't be a gas counterpart in the Super Duty lineup. A diesel is so much more economical in the sense of burden of power and mileage while under load.