If you're real serious about pulling the Cambridge, get the best for now. The Duramax 3500 with the most powerful HP and tourque. The GCWR for this truck is a whapping 26k and will handle the 5er well. Now, since GM is a step ahead of Ford and Dodge, wait amonth or so and one of the other manufacturers will outdo that, it is just a matter of time. In case you are wondering, I'm making fun of who has the most powerful truck, it depends on your own preference as to what truck you drive. I personally like different things about the big three, but I like the GM employees discount a lot. But whatever you choose, make sure of the pin weight, go with at least a 350, a 450 would be better if you plan on towing a lot.