Their inlines are a rabbit hole of great dimensions.

The common Series 1 I-6 for commercial rigs up to Class 5 'innaday' were the 228-270-302 inline - all gas.

The latter were popular with hot rodders, and in some regions, banned in sprint/open wheel along with the Ranger aircraft engine.

Beyond that were a two series of even larger gasoline inlines of similiar architecture (but larger and not interchangable) ranging up to 503 (!) cubic inches, found in 600-, 700-, 800- and 900-series GMCs. These engines were also used in other stationary and industrial applications.