Starter pinion gear

[DriverJon]

I have a situation where I've rebuilt a early 2L motor (72-74) to put in a 77 Spider. This creates a problem in that the ring gear on the flywheel has the early 130 teeth, as opposed to the 131 tooth one that was used sometime after 75.

I'm trying to find out how to identify starter pinion gears, since from what I hear, the 131 starter with it's slightly smaller gear will be a loose and possibly quickly wearing fit on the 130 t ring gear.

I have a starter that MAY be from the original engine, I bought a new (unknown) pinion gear for a starter at a swap.

So far, I haven't been able to get definitive info on how to tell what's what. I've measured them, there is a difference, but it's so small I'm still not sure. I also got someone to measure a type 4 starter, which is supposed to be a good fit for the early ones, and it seems to compare with my old starter and new gear.

Does anyone know how to ID these things? I have a few Bosch part numbers.. Has anyone had experiences with swapping starter types, and what happened?

The starter is a bit easier to swap with the engine still out of the car, and I'd prefer not to tear down my existing one to swap the gear for the wrong pinion.

Jon