I have been looking at the 6.4 as well and am disappointed that an EGR cooler was added to the gasoline engine - I was considering getting away from the complexity of the current diesels by going with gasoline.
For those of you with this gasoline engine, I have heard that the torque is not there at the lower RPM's, so you have get used to it keeping higher revs. I'm looking at Ram 5500 chassis cab which will exceed 20K lbs GCW with my current setup and in the future I will easily see a 26K lbs when I upgrade the truck camper and trailer. Am I asking too much of this gasser since I regularly climb 4000' elevations from sea level?