I enjoyed reading “The Refit That Sparked a Revolution,” but there was one big mistake in it. The Gray Marine Diesel was not the precursor of the Detroit Diesel. GM started putting Detroit 6-71 diesel engines in trucks and buses in 1938. When the war came along Gray Marine Marinized the 6-71 and built them under license from GM as a way to meet the production capacity needed for the war effort. (Much the same way Ford built Jeeps under license from Willys, and Chrysler built Rolls-Royce Merlin aircraft engines.)
The Detroit Series 71 engines all used the same unit cylinder assembly and became the most prolific series of diesel engines ever built since they were available as inline engines of 1,2, 3, 4, and 6 cylinders as well as V6, V8, V12, V16, and V24 configurations. Since they were a sleeved design you can readily replace everything but the crankshaft without removing the engine.