Thanks Jonathon. No, I never considered the 6.4 gasser. I thought that since I was underpowered with the 5.7, that I would swing to the other side and get the most power. At 385 HP and 930 lb/ft of torque, the power is eye popping and really amazing. And I am sensitive to fuel economy, and the Cummins is the best in that respect. Cost of fuel, initial buy-in of the truck, potential maintenance costs don't concern me. I wanted the power, fuel economy, and well, I just love diesels. My last was my Mercedes Benz E-320 CDI turbodiesel, which was the last of the iron block straight six turbo diesels from Mercedes. Amazing engine--power and fuel economy. I miss that car...my current gas E-Class Mercedes is no where as satisfying to drive. There is just something about driving a diesel... So, no, I never considered the 6.4. I think that a 2500 with a Cummins will not have very good payload at all since the engine is so heavy. Need the 3500 if you go diesel and want a TC.