Not sure what the Big Boys Section is as have yet to find it, however, I think I have found the answer from a bloke in Victoria. Evidently it is unusual to have a 57 year old tractor that has the original starter motor in it but this one does. It appears that when they started making post manufacture parts they made the new motors with only 9 teeth but they were machined so that they would still mesh properly with the original ring gear. So I have been told to whack in the Fergy and it all should be fine.