I now have the two main bearings and the front seal. (The bearings are the 6203 C3 type and the seal is genuine Stihl).
I'm ready to go looking for some aluminium stock rod to machine the prop driver.
What sizes is the one you picture in post # 39 Zagnut? It looks like I should start with 50 mm diameter stock.
I will start by machining a drilling guide out of some 8 or 10 mm thick steel plate. This is because I will not have a means to set up a drilling jig to drill the 6 prop retaining holes while the hub is still in the lathe chuck. I will rely on the guide, with it's 10mm centre hole, to drill the six holes in a drill press prior to hand cutting the threads. I assume from the chart above that 5mm machine screws will do the job, is that ok?