Early Rams in 07 were still the 5.9 Cummins. The newer emission laws kicked in with vehicles produced on or after 1/1/2007.
There are a few reasons so many Fords diesels are for sale with the 6.0. The first is that they outsold the GM and Dodge diesels in those years 2 to 1 combined. The second is that they are ticking time bombs. Those that never had a problem are few and far between, and when they do look out $$$$$$.
Sorry Ford guys, I really wanted one but the evidence is over whelming.