Yes, they are the same..1937-40 casting number 598309
1937/38 p/n 598308
1939/40 p/n 838903.
The pulleys are different that's why there are two different part numbers with the same casting number.
1937/38 Pulley stamped 838764
1939/40 Pulley stamped 838905
Hope this helps,
Mike B
