GM used the 454 (7.4L) Gas engine even as far back as the 70s possibly earlier, in their trucks so the Powerstroke was never the biggest engine put in a truck. The 496 V-8 is just a bored out 454 so it's an excellent engine and been proven reliable over the years.

 

Well, if things change as often as they seem to at GM, it seems likely that by the time they finally decide what the hell it is they're really going to do they'll have changed the projected line up to something much more dull and... GM-esque.