starter motor

If you're having problems with your pre-engaged starter I would suggest that you take it to a local starter shop and get it rebuilt. That would be cheaper, I think, than buying a new one or trying to cobble in an inertia starter.
The pre-engaged starter is a much better deal than the inertia starter. I've got one on my autocross car that was custom built for me by a local starter/magneto shop using a Nippon Denso starter from a Chrysler minivan.
They can be interchanged -- IF they have the same tooth count on the Bendix gear. The pre-Verto and Verto flywheels used a different tooth count. You can tell which clutch you have by the location of the slave cylinder. On pre-Verto cars, it's mounted horizontally to the top of aluminum flywheel housing. On Verto cars, it's mounted at a 45-degree angle on
a bracket attached to the domed flywheel housing cover.
If I'm not mistaken, all Verto cars had a pre-engaged starter but you can also get them for pre-Verto cars.
JL