Adrian, yes to your questions, I was directing my comment more at the bolt pattern for the starter motor. Different flywheels will define the length of the throw required, as well as the teeth numbers. As JTL comments, the combinations are large and if you cant match the numbers on the starter motor, you have issues.
A good contact as supplied by JTL should be able to tell you what you require in teeth and throw, from your old one, you then have to find one with the right hole pattern, thats the tricky bit.
