OT: Diesel pickup truck recommendation

[Gsinill]

Retirement is getting closer...
Once we get there we plan to travel the country with a trailer.
The one we are eyeballing is around 8,000 lbs., a little more than what my current diesel SUV can handle.

I am a car guy but know nothing about p/u trucks.
Given their cars' reputation, I'd probably rule out anything from Chrysler/Stellantis, which leaves Ford and GM.

I assume asking for opinions on those 2 ends in something similar to a Shimano vs. Campagnolo debate

The best info I got so far is from my neighbor's dad who runs a hobby farm.
He swears by older Fords. He got 3, all one ton and he insists I shouldn't get anything smaller. He also mentioned that the older models (pre-2006 I think) are preferable due to a less complex emission system.
This makes sense, but I would like to gauge the trade-off carefully as someone who cares about the environment. I also assume that MPG of a modern truck is significantly better than what you get from a 20 year old engine?

That's all the info I got so far, lots of research on the web is next, but since I know that we have quite a few folks with trucks on here, I thought I'd check.
4WD is a must.

Any input is appreciated and thanks in advance.