We have a lot of 6.4 engines at work. They are a orphaned engine, only a few years made. I would not recommend one, our trucks are always up at fleet for issues. Of course our newer trucks are 6.7. If I was in the market I would go with that engine or duramax or Cummins. That's my suggestion, I didn't want to deal with regen issues and Dpf so I bought the gas version. Either way take your time, a lot of these trucks have had programmers and delete kits. Just take your time find a great diesel mechanic and get it looked at prior any purchase. Good luck.