I have the 3.6 V6 in a Dodge Journey and the engine is adequate for that vehicle but I think it would be totally overwhelmed if you put it in a full size pickup.  The engine generates some decent fuel mileage but the torque and pulling capacity is very weak in my opinion.  My Journey struggles to pull a empty 6x12 single axle cargo trailer.  I have 75,000 miles on this 2013 model with no issues with the engine.  Without question, I think you would be happier with the hemi and probably wouldn't use much more fuel then the V6.  Maybe I missed the point, are you talking about the eco diesel V6 or the 3.6 gas engine?