I own one and very partial to it...a Ram 2500 Megacab 6.4L. It sits on the LWB 8 feet bed chassis. The room in front of the second row is unbelieveable. If you do pick up a 4th gen RAM (2014+), I would highly suggest the 6.4 L Hemi. The 5.7L is adequate. It would makes less horses and torque than its big brother. The 6.4L is the workhorse of the 2. When I see this generation for sale in the used market, the trucks tend to be equipped with the 5.7L; I think owners tend to hold on to their 6.4 trucks longer. Resale prices seem to be much lower for the 5.7L 2500s too.
Again, 2014+ Ram 2500 6.4L Megacab for the win. ;)