I would avoid ford 6.0 and 6.4 engines.
The design life on the pickup diesels is in the 220k-250k range. Some obviously do much better than this but it isn't a given that a diesel pickup will last 500k miles.
At the last job I worked we had three gm 2500hd trucks two duramax and one gas 6.0. they all had about 200-250k on them. One duramax ran great, the other ran like total garbage and had already had to have 5k in fuel system work done on it. The 6.0 gas also ran well.
I wouldn't consider a pickup gas or diesel with 100k barely broken in. I would consider it 40% used up with it's best and most reliable years behind it.
The issue with diesel ownership is that the recent model years have the potential for very expensive 10k+ dollar engine and fuel system repairs if something does go wrong. Not saying it will but know that the repair cost can get very high if something does go wrong.