Back in the day, the big three had special truck-only engines. In fact, in many cases, the truck engines were pretty low HP inline 6s. I don't really know the engine history for this class of truck though. In a way, this is a new class so I guess I'm lost.
Anyway, GM's been doing truck engines from car engines for decades in stuff at least up to the 1-ton weight class. When Ford had pushrod stuff, they did the same thing. And like GM, the big block stuff was not being used in cars after the late 70s and moved to truck-only duty (460, 454). Not sure about Chrysler though. Did they even have the 440 in the 80s in trucks? I have no idea.
Perhaps the exercise should be to figure out the first car-based engine that was used in a 1-ton truck. Probably the late 60s.
Fun fact: even GMC had their own engines if you go back far enough. One such beast was a 302 cubic inch inline 6, which was pretty stout.
http://en.wikipedia.org/wiki/Chevrolet_ ... MC_engines
http://en.wikipedia.org/wiki/GMC_V8_engine
Before diesels were as common in trucks as they are today, there were some pretty big gas engines that were truck only. Your diesel option would have been a Detroit 2-stroke, at least for GM power.
http://www.curbsideclassic.com/blog/the ... -1600-rpm/
That displacement, power, torque and RPM is pretty reminiscent of a diesel and probably moved the trucks along just fine.