For a big bolt I would go with the 5.9 for sure. A 4bt will be underpowered compared to the 5.9, not to mention all of the goodies you can bolt on a 5.9 cummins. I would go with a 12 valve for the fact that they are all mechanical and can be turned up with just a turn of the star wheel(air fuel control). I have one in my '98 dodge 3500 and it will pull just about anything you can hook to the truck. If I were you I would go find myself an old dodge 1-ton and steal the engine, NV4500 trans, and Dana 80 rear end.
