I only have experience with the GMs. It's my opinion that the 1500s need the 5.3 and the 2500s need the 6.6. The 4.3 is quite underpowered for practical use unless driving to get groceries weekly. The 2500 reg cab long bed I had with the 6.0 was a chugger and got awful fuel mileage. For a truck that's on the road hauling and pulling the 6.6 is stronger and more efficient. I have a 13 ext cab long bed now and load it to the max pay load in the bed as much or more than I tow a heavy load. The 6.0 got 9 mpg. Now I'm still 13-14. The warranty is almost up and it's acting silly. Been in regen for two weeks now. Going to delete the emissions and tune and will see an increase in mirage.
