After talking to Snyders they recommended I not swap in a starter with the 5/8 shaft. I was told that the flywheel for the multi disk clutch is a different profile and that the 5/8 starter drive would jamb against the early flywheel and lock up the whole starter drive and flywheel.
What most folks would do is remove the early flywheel, flywheel housing, clutch and transmission. Then replace with the later flywheel, clutch and transmission. That's more work and expense than I wanted to go through if I could avoid it.
I did locate an early starter drive. I will be trying it out probably next week when it arrives.
Thanks to everyone for the help. I learned a lot about '28 model A's. There were many production changes in the early years of A production. I cut my teeth on Model A's but I'm a V8 guy.