There closest years to 1947 that Chevrolet had a green engine were (
supposedly ): 1924-28 4-cylinder gray-green/dark green; and, 1954/etc 6-cylinder 261 green (alpine green).
Any engine as old as that 1947 engine has most likely seen at least one (and maybe several) rebuilds. If you were doing a rebuild on a work-truck engine and you wanted to paint it, great care in choosing/buying original color paint was most likely not a priority.
