I've assembled the RobbMc starter an checked clearances with the ring gear on the flywheel. It all checks out correctly. Here's the RobbMc starter:
Here's the gap between the flywheel face and the end of the starter pinion:
Finally, here's the tooth engagement of the starter pinion in the new ring gear:
See the paper clip in the picture. This confirms about 0.030" gap between the end of the pinion tooth and the root of the ring gear tooth. I also measured the backlash of the gear set to be about 0.035". According to Robb, these are all within expected ranges for proper pinion to ring gear engagement.
The engine is not back in the car yet. When it is, I'll post my comments on the function of the starter.
Chuck