The original early '50s F series Toyota engine was loosely based on the 216/235. The differences between the F ('55-'74) and 2F ('75-'88) are essentially the same as the differences between the 216 and 235.
From Wikipedia...
The F engine block, crankshaft and lower end assembly is loosely based on the 1939-63 G.M.C. L6 OHV 235 engine but with a taller deck (rather than the similar but smaller Chevrolet 1937-63 Gen-2 216 L6 OHV engine), and built under license. The cylinder head and combustion chamber is derived from the Chevrolet L6 OHV "stovebolt" engine, slightly scaled up. The general idea was consumers would feel comfortable with the engine since it was a familiar design and had a proven track record. None of the bottom end of the engine is interchangeable with these engines.
Type B was produced from 1937 through 1955 as a more technically advanced version of the Type A. The design was based on the Chevrolet 207 engine, and built under license but with metric dimensions and minor revisions to suit the local market. It had a four-bearing crank and shaft-mounted rocker arms, as did the Chevrolet engine.
The Type B was succeeded by the similar 3.9 L Type F in 1955. The Type F is based on the larger G.M.C. 1939-63 L6 OHV engine in the same way that the Type A and Type B were based on the Chevrolet engines of their times.
