I have no knowledge of this topic; however, here is some documentation:

42-47 - through the water jacket
http://chevy.oldcarmanualproject.com/shop/1942_47/4247csm621.htm

1947 - through the water jacket
http://chevy.oldcarmanualproject.com/shop/1947truck/47ctsm0633.htm

1948-50 - through the water jacket
1951-?? (1951-1953, maybe) - through the crankcase
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0638.htm