I would definitely go with the LB7, assuming it came out of an '03 or '04. Way better engine plus it doesn't have the emissions controls the LLY must suffer. You can turn well over 800 hp with a LB7, not to mention the dyno killing torque. Those numbers make me rethink the little 3.9 all the time, but the old p7100 pump on the cummins is hard to pass up.

1953 3600 w/ full pressure 235
"Quando Omni Flunkus Moritati"
--If all else fails, play dead.