ognend, based on your opening post IMO you'd be better served going gas. The only question you seem to have is whether you'll be giving up "power" by going gas.
The 6.4 Ram Hemi and 7.3 Ford Godzilla gassers both have 400+ horsepower. That's more HP than a standard Cummins (370-385hp). A 400+ HP gas engine will pull a 11k trailer up a 7% grade at 60mph (based on personal experience). The caveat is you'll be in 2nd or 3rd gear pulling 4.5-5.5k RPM (near redline). Although massive torque at low RPM (i.e., turbo diesel) gives the impression of effortless and unlimited power, all said and done HP (along with proper gearing) ultimately determines how much work actually gets done, not torque.
I currently drive a Cummins. I absolutely love "how" this engine tows heavy. However, if I were buying a new truck tomorrow I'd probably go gas (mandatory options: an 8-10 speed tranny and the lowest available rear end ratio).
