[VetteVet]

If you install the solenoid and disconnect the copper bar that goes into the starter field to prevent the starter from turning, you can make a jumper from the positive cable to the S terminal and you can engage the starter drive gear to the flexplate and see exactly what's happening. If you have the coil ignition you should disconnect the "I" terminal to avoid sending voltage to the coil.

It's possible to pry the gear out into the flexplate manually but it's hard to hold out and see what you have.