Beginning in 1920, GMC and Chevrolet trucks became largely similar, built as variants of the same platform, sharing much the same body sheetwork, except for nameplates and grilles — though their differences, especially engines, have varied over the years, according to Wikipedia. GMC advertising marketed its trucks to commercial buyers and businesses, whereas Chevrolet’s advertising was directed toward private owners. Beginning in 1928, GMCs used Pontiac’s 186 cubic-inch six-cylinder engines in their lighter trucks. Medium-duty...