I have been contemplating buying an 04 or 05 dodge ram 4x4. The hinge in my choice is what frame I will need for my build. I have spent the last few months researching different small displacement diesel engines for one sole purpose... MPG. I will be driving 2000 miles a month for work. There are many strong options, with the Merc om606, Perkins 6.354, Cummins 4bt (ended up with mixed feelings), and even the Detroit 453t (who doesn't love a screamer?) was under consideration. My biggest concerns are weight and efficiency. What effective hp and tq figures will I need to get better mpg than the stock hemi/24v? What could I expect? This isn't going to be used for anything but traveling on interstate (80mph in my state), so no towing or racing. Are there engines that would do better for me? Any incite would be appreciated.