I thought about the 6.0, but I just don't want one of those. I can get the L33 with low low miles for $1k. I think gas mileage would suffer too much with the 6.0 and beyond that I would definitely have to upgrade the 4l60e and the rear end. I'm thinking of the truck as a whole if I swap the engines over and if I go the 6.0 route I doubt the current transmission will hold up long. Now with a few mods it should hold up well behind the 5.3 for awhile until I boost it.