boils down to the same issue that always comes up with a 6.2L diesel swap. hp vs torque.
I say do it. im a huge fan of my 6.2L diesel, but i dont mud bog, or sand drag, or any of those other events where a 496 big blocks rule. I drive my 5200lbs truck like its a 5200lbs truck. A cruise in the slow lane, i accellerate as fast as i want to without causing a traffic jam, and even with 3.08 gears ive never had to stress about merging into high speed traffic from an onramp.
Getting 22mpg out of my rig is also nice. and the torque when offroading is darned impressive to me. I can normally make it anywhere ive tried to go in 4 hi, and in 4 lo it will climb trees. am i still planning a turbo install, absolutely, but thats simply a "want" in the same category as my 1 ton axles and NV4500 swap. as it is right now it certainly covers my truck needs.
I think if you were replacing a stock, or mild 350 with a 6.2l diesel, you would be very pleased with the result. if youve got a high performance mill, youre gonna suffer from slug syndrome.