http://www.vanpeltsales.com/FH_web/F...rankpulley.jpg
I think Kube has it right. The 1939 Standard Ford (with the regular 85 hp V8) still placed the fan blade up on the generator pulley, so there was no need to mount anything to the crank pulley. Because the crankshafts grew in length for 1939, they had to have the “extension “ on the front side of the pulley to fully cover the added length of the new crankshaft.