One of the diesel or 4x4 magazines did a test with a 6.2 build up and found that it is limited by the very, very poor breathing characteristics of the head design. It will only make so much power and that amount of juice isn't worth the squeeze. They're a good engine, but you will only get so far then that's it. Any big block would be fantastic, even a 366 or better 427 truck engine would be good as they'll start with roughly 50-80hp more. The truck engines are beefy with all five mains being four bolt, steel crank, heavy duty rods, four ring (diesel like) pistons. They don't make a ton of rpm in stock form because of heavier truck use, but are good engines.
I think a twin turbo set up is awesome (fun for bench racing, of course!
) but in just direct engine to engine comparison, you'll have more power, low octane fuel, more rpm available, more power, and no complaints on torque. The TD engine usually have better heads than the 454's too. A LOT of later model 454's have the peanut port nearly round small intake port where the TD's have the larger ovals. If you're in love with a supercharger idea, both mentioned engines are perfect candidates.
Are you the same guy that could not get the truck started yesterday in 30 degree weather? It is colder today then yesterday. I would put twin turbos on it and either injection with a super charger like the big trucks have. Then it will start and smoke the tires all at the same time.
Look out you will go up one side of the road and down the other.
