Just read an article in a diesel magazine and they recommend that ANY diesel have a separate fuel water filter system installed. Yes all the new ones can have water in fuel issues, so they make an across the board recommendation.
Also the 6.0 engine did get a bad rap but many are now reconsidering the engine as a few upgrades to head gaskets, EGR and oil coolers will take care of the biggest issues they had. At a couple of the recent truck competitions the 6.0 have out performed many newer but then they have all the fancy upgrades. The FICM is also an issue but most things can be corrected for less than $5K in general. The 6.4 had water pump issues and the 2 n 1 turbo left a lot to be desired just as it is on some of the newer models. Thats why the new fords have gone back to a single turbo. But as noted you are looking at a minimum of a 12 year old truck. Mine is an 04 have taken care of the egr/oil cooler and head gasket & studs. We dont tow anymore but it is still our vehicle of chice for travel, big roomy and comfortable. Dont miss any of the new toys that are installed in newer models.