If you're considering GM, take a look at the weight capacities on the 1500 HD. The hd comes with extra weight handling stuff -- x-tra radiator cooling tran cooler etc -- plus 4 wheel Disc Brakes, Add the tow pack and you are ready for a lot of towing capacity. (without looking it up, I believe its 14,000 or 16,000 combined weight, truck + trailer) I have the 6.0 4x4 and mileage is an issue -- ALL THE TIME -- not just towing. A friend has the 5.3 2wd and does worse towing but about 20% better without a trailer. 6.0 does a better job, but I have to feed the beast 24/7. His 5.3 is adequate and more economical without the trailer. Also, he has the 4.11 rearend and I have the 3.73 rearend
budc