The 6.4L Ford diesel used from 2008 thru 2010 was not much better than the 6.0 in terms of reliability. It was much more expensive to fix. It is also known as being rather thirsty on fuel.
My boss bought one not long ago for about $10,000. It wasn't long until it wasn't running right. The least expensive repair quote was $8,000 for a new engine. The truck was not repaired, it was sold as is and they purchased something else.
I don't know the specific problems it had. I just heard our fleet manager venting about it. The boss likes cheap trucks. He's also purchased 2 Ford 6.0 trucks with disastrous results. We've spend more money repairing them then they cost to buy.