Here is a couple interesting quotes:
Arguably the most famous engine Cummins debuted in the second half-century was the B5.9 in 1984. A success on its own, and eventually spawning a 3.9-liter four-cylinder version, it was Dodge's 1987 decision to install it in the D/W series that really got it going. Dodge wanted it for "its toughness, durability and fuel economy," and initially thought they would need 20,000 engines a year. That quickly proved an understatement--only 14 years later Dodge/Ram had used a million of them.
And
Had early Ram enthusiasts invested $24,000 in Cummins stock rather than a 1989 Dodge Cummins pickup, 30 years later they'd have about $475,000 (based on share price and adjusted for splits).