I currently own a 2014 Ram 1500 5.7 V8 and am considering trading this in on either a 2500 6.4 HD Mega Cab or 2500 Cummins. I tow a 30' camper with about 6,500 dry weight and probably 7,500 when packed. My current 1500 get a terrible 6mpg - 7 mpg so need to upgrade to a bigger truck. Looking for advice on my upgrade and what the mpg will be on either of the two mentioned above 2500 would be? The 6.4 HD has an axle ratio of 4.10.