Triumph 4 cylinder with the SOHC 4v valvetrain. It's sibling, with only 2 valves per cylinder, would go on to also be a pioneer, as a Saab turbo. Unfortunately, the British manufacturing tooling was not very good so they couldn't consistently hit power targets, which is why the car was called the Dolomite Sprint instead of Dolomite [theoretical horsepower].

Truck would be the 2.9L DOHC by GM. It made about 185 hp. Was used in the Colorado.

Heavy duty would be the 8.5 Detroit Diesel. Total nuts. Unfortunately, most of the buses with it have been phased out, so while I've probably ridden one as a kid, I don't remember how bad the vibration was.

6 cylinder would be the Daewoo 2.5L I6. Apparently it was shorter than an Ecotec L850 4 cylinder.

Then you have GMC's big block V6s, ranging from 5L to 7.8L. 60 degrees, soon after Lancia came out with the world's first serious production V6.

Then you have the 12L 90° diesel V6 from Mercedes, was in their semi trucks. They switched to I6 later, partly because EGR is easier to manage if you have one hot side and one cold side, or so they say. Also, they stopped making V8s.

8 cylinder... hmm. Not that I actually know much about it, but Pontiac had a flathead straight 8. Cheapest car with one.