Admittedly I am a RAM/Cummins owner, but just reflecting on all of the tow vehicle problem postings I have read on this forum over the 9 years I have been on it, it seems to me I can remember some postings on Ford Diesel problems and next to nothing on RAM/Cummins problems.
I have 180K miles on my 2004 RAM/Cummins 5.9 6 cylinder. I have replaced water pumps twice (twice because the mechanic went cheapo on the first one), and just had most of the engine compartment components of the air conditioning replaced today, although the Freon leak was just in the compressor. That and having the valves adjusted at 100K is all the major maintenance it has had. I use XDP Diesel Power Plus fuel additive (
https://www.xtremediesel.com/xdp-diesel-power-plus-fuel-additive-xtremedieselcom ) and installed a cleanable, reusable, oversized air filter that completely fills the intake air box (
https://www.dieselpowerproducts.com/p-10276-aem-dryflow-air-filter-03-12-59l-67l-dodge-cummins.aspx ) . Oh yeah, I've changed the serpentine belt twice now just because I want to do my best to prevent getting stuck in the middle of nowhere. The belts were probably perfectly fine.