My source is the 1929-51 Parts Book, group 0.033.
If jimgmc's Hollander Manual is correct (I don't have the 838101 for 1937 or 838710 for 1938 in any of my sources), then there were changes made each year making the previous block obsolete. The 1939 block became the replacement block for the 1937/38 vehicles as evident by the 1951 Parts Book grouping those years together.
Look for the casting date code on the passenger side of the block...should be a letter and 2 or 3 numbers with screw heads on either end.
Mike B
