M38A1 front pulley?

[Jack Innes]

M38A1 question; I have discovered the nut that holds the crankshaft pulley in place is missing from my newly acquired M38A1 & the pulley is loose on the shaft. This appears to have been like this for some time. It has about 1/4" movement radially which indicates to me a worn keyway & key. I can deal with that but I do not know if the nut is an odd size or if the shaft has some distortion. A 1" NF nut will start but becomes alarmingly tight after about one turn. Does anyone know the thread size? The pulley may need to be replaced. I am sure I read that the pulley & nut are are the same parts on both the flat head & the F head engines,; is this correct?

Secondly could this allow the timing gear to work loose on the shaft as well? The distributor cap shows evidence of the timing being off but perhaps this was a previously corrected situation.

Thank you for any input.