i have seen starters for hysters and yales both come as 9 or 11 tooth starters, Yale actually had both for their Mazda engine. As long as the teeth match up to the ring gear teeth and you do not get any grinding when turning the engine over then its good to go.
If you do get a binding like the starter is working too hard then yes , to answer the question about the shimming. All GM starters that mount this way require a shim if the Bendix teeth set too deep into the teeth of the ring gear.
If you want to know for sure how the bendix is running with the flywheel ring gear just put some prussian blue on the teeth and run it around a couple times. Remove the starter and look at the pattern.