TS,
I don't know if this will help but I'll offer it up.
I have attached photos of three different starters.
Small geared starter #1005 824 071. Also has a second # 1073017 ??
Large not geared starter 0001 211 987
Large not geared starter 0001 311 110
The two large starters appear to be the exact same size but have different solenoids. One came off of my 74 2L Spider and both fit and work on that engine. The ring gear is 130 tooth model. I tested theses on the engine while it is on the engine stand.
The small geared starter is the type that is supposed to only work with a 131 tooth ring gear. I have two of these. I tested both on my engine while it is on the engine stand and interestingly enough, they both worked without any grinding noise.
I know this doesn't help you but may be why there are so many different stories out there.
If you have the small geared starter, you may want to order a 131 tooth ring gear from Spruel and have it installed on your flywheel. Perhaps you could return the fly wheel and ring gear you got from group 2