I feel your pain...I've got the same problem with my F-250. I really want a regular-cab Dodge, but there's no way I'm ever getting rid of this truck for personal reasons...but there's a reason I named it the Nimitz

BTW, not all people are selling trucks due to problems. Many people just decided to buy new (enticed/seduced by claims of more power, comfort, etc) and figured they could get more on the private market. In fact, some of these people have actively regretted selling their old trucks...this is especially true on the Ford site; quite a few people traded perfectly good 7.3l's in for the new 6.0l and are having endless problems with the 6.0l... Getting records would be a good idea but assuming you've got an idea on the vehicle history, I really wouldn't be concerned at all about a 12 valve Cummins. I will admit, though, that some concern could exist about the 24 valve; if the lift pump on that engine goes out, the injector pump often follows (doesn't like being run dry)...