Actually, there were six different models of US-built Sherman tank with gas and diesel engines (and one Canadian-built model):
M4 — Continental R-975 radial gas engine
M4A1 — Continental R-975 radial gas engine
M4A2 — GM 6046 diesel engine (joined 6-72 engines)
M4A3 — Ford GAA V8 gas engine
M4A4 — Chrysler A57 Multibank gas engine (3 straight six engines joined)
M4A5 — No US production; 188 built in Canada as Grizzly I with Continental R-975 radial gas engine
M4A6 — Caterpillar RD1820A radial diesel
Typo: “M4A2 — GM 6046 diesel engine (joined 6-71 engines)” vice “...(joined 6-72 engines)”.