I have sealed starters on pickups and farm tractors since the 50's because that's what the old timers did. On the dirt roads of the day they were subjected to a lot of dust. I recently rebuilt a starter on a 1950 John Deere with a Delco starter that had a gasket. Was it original? I don't know. I just reused it. Had it not had a gasket, I would have used duct tape. We buy 42MT starters for our over the road tractors factory rebuilt. I have never looked at them. Generators had fans for air flow any way.
