Mr Truck reviews the 6.4L Hemi. Although he didn't have anything positive to say about this engine's power in the RAM chassis cab, his comments for the 6.4L in the 2500 is pretty good. Link
We tow a 2 horse trailer with a 7500 GVW and we live 2 miles from town so most of our trips are less than 10 miles. The 6.4 with will likely be our next truck.