Pickups aren't built to last forever anymore. 20 years at the most before the electrical bugs consume the trucks. The emissions systems on modern diesel engines are killers. There's still some good older stuff out there. I'd pay $5000-$7000 for a perfect 4x4 diesel pickup that is 30-40 years old and is in like-new shape. Hell buy a couple trucks and have a backup. Parts are dirt cheap, and diagnosis can be done in a barn. I'd never spend $50,000-$60,000 on a modern diesel truck more complicated than the human body.

I wouldn't buy a new one for a farm workhorse.

The farmer near me has a 351 powered F250 4x4, it's a 1977, 4 speed truck, over 400,000 miles on it. The original clutch lasted those 400,000 miles, all local, doing hard work. He just recently rebuilt the motor and changed the clutch even though it still had life in it. The frame and body are in excellent shape, it had 1 repaint. The truck will probably last another 400,000 miles.
^I'd look for something with this simplicity and build quality.

 

With the price of a new truck today , I would rather spend the money on repairs on my current one , anyway . And the older vehicles are a whole lot easier to work on .