Lets go back to 1988 for a moment. (some of this stuff is in old TDR issues, too).
Ford was using the bane-of-farmers International Harvester engine. Its main claim to fame was greater power and durability than the sorry excuse GM ws using.
For their part, GM proudly went from the sorry Olds diesel to one made by a presitgious GM-captive company, Detroit Diesel. The rest of the story is that GM ensured the failure of both engines by letting the bean counters run rampant. The Olds had to be a super cheap adaptation, and GM had taken away the Olds crank forging cacility in 1967, so Olds was stuck with a cast crank and four head bolts per cylinder. The Detroit Diesel was cursed with cast crank, odd spaced head bolts, and numerous other "oddities" including indirect injection whose design ensured that the heads would crack with regularity. I was told that pallets full of heads went to Iraq in 1991 to accompany the Hummers.
Against this backdrop of engines built to the lowest possible price, a couple Dodge engineers worked with a couple Cummins engineers without sponsorship. The 4B engine wasn't impressive, so they shoehorned the 6B into the Dodge pickup. They quickly found that some parts such as universal joints were marginal. They sold their project to dodge and Cummins, so in 1988 Dodge agreed to buy 15,000 engines, over the next several years.
History has not recorded the feelings of Ford and GM but it takes not too much imagination to believe that they were disgusted and outraged that Dodge was using an engine that was far too good and long lasting for a pickup truck, eclipsing their efforts. Prior to this, they felt they had Dodge covered. In fact, Dodge was a very small player in the pickup market; I have heard numbers in the 3-5% range for the relative number of trucks sold.
Lo and behold, Dodge had all 15,000 engines pre-sold with firm orders by Christmas, 1988. By begging Cummins, they were able to get 16,700 engines for the 1989 model year. History was again made this spring, with one million Cummins engines being sold to Dodge.
Ford yells "POWER STROKE" and Chevy hollers "DURA MAX" in response, to get customers' attention. Dodge quietly puts a small emblem on the fender that says "Cummins. "
Oo.