Prop shafts are all the same part number up to KE3 and WG4
Gear can be pressed off after pin is driven out. Twins use 14/19 gear set.
Last time I needed a prop shaft I got it from Tom Thuerwachter in Fon du Lac

I have a prop shaft someone made from a bolt. Not a good job but it
apparently worked as it came on a motor. If you can use the old prop shaft
for measurements making a new one from a 1/2" ground stainless bar stock is not a serious lathe project. I can hear the groans now...who is a machinist?

If you are in Southern Michigan, Northwestern Ohio or Western Ontario you are not far from Yack Arena Wyandotte, Michigan
25th annual North American Model Engineering Expo will be held there
this week end April 26 & 27 2014...there you will see impossible machining projects up close and get to talk with their creator.
Craftsmanship is very much alive and well despite reports to contrary.
Louis