FORDFirst gen Ford 6.9L would go about forever. It isn't uncommon to hear about one with more than 300K on the clock. They lived so long because they were laughably understressed (and horrifyingly underpowered).
The in-between 7.3L IHI-turbocharged diesels should probably be avoided unless you are into oddball stuff.
The 7.3L Powerstroke is a proven commodity - strong and reliable. Gale Banks made his name in the diesel market with his famous no-smoke 700+ lb-ft torque PowerPak kits for them. Depending on the year, the rest of the powertrain may be a little soft around it. Early transmissions had a nasty habit of failing under all that twist, but there are people who specialize in making them bulletproof for a reasonable amount. Same with u-joints.
The 6.0L had problems early on but was okay after they got the issues lined out.
I understand the new 6.4L sequentially turbo'd version is having some issues, as well as being a bit on the thirsty side.
DODGEWhether the early mechanically injected or later electronically injected versions, the Cummins engines are about as bulletproof as it gets.
On early diesels that retained the old body style, the powertrains were rock-solid for they were, after all, based on the three-decade-old PowerWagon chassis that was first developed for military use. The bodies, however, were rust spots and rattles waiting to happen. If you got the switches and controls to stay in place - much less actually work - for more than a few hours at a time, count yourself lucky.
The first gen big-rig styled bodies were a little better with the rust and rattles, but controls are still an issue. The second gen bodies were a little better, though they had some problems with tranny synchros in the 5-speeds.
The chassis and controls just prior to the latest redesign seem to be holding up well. My brother has one and it hasn't laid down yet.
Don't know a darn thing about the newest ones.
CHEVROLETNot very familiar with the first Chevy non-turbo diesels, although I understand that many a mechanic made a decent living swapping them out for 454's.
The in-betweener turbo diesel was a bit of a conundrum. I don't recall anyone having much problem with thme, but then it seems neither were they all that popular. To me they made too many strange mechanical noises that were not "diesel-y", always sounding like they were on the verge of coming apart.
The latest engine seems to be a hoss. My brother has several friends with them and they all like them. Plus, they don't sound quite as strange any more. In fact, they are almost
too quiet, not sounding much like a diesel at all.
Brad
p.s. - You could always get a used up diesel Rabbit pickup. I hear they can be had pretty cheap...
