This is my "red-neck" knowledge of the starting system.

Most people rely on voltage as indication that a battery is good. Actually, it takes voltage and amperage to spin a motor. A battery may have 12vdc +, but not enough amperage to provide the power to the motor thus P (power)=I (amperage) x E voltage. Thus, the importance of load testing a battery when troubleshooting a system.
A poor connection may also provide a good voltage indication but fail (loose electrical contact under load. The battery cable terminals are a common failure point connecting to the posts. Thus the need to check all electrical connections and wiring to verify adequate power is delivered to the electro-mechanical device (solenoid and starter). Any circuit is not complete without a ground, thus a check of the wiring must include all of the wiring and connectors from the battery to a ground. Professionals have equipment to 'megger' the wire to determine a bad insulation, ammeters to verify current draw, as well as voltmeters for voltage verification. The Ohmmeter is used to determine a short or open to ground, as well as the resistance in the system (wiring and devices). We can perform most of these checks with the inexpensive VOM or Multi-meter and a very small amount of the vast knowledge an Electrical Engineer must have.

Once the electrical system has be verified good, then the electro-mechanical devices (solenoid coil and starter windings) can be tested with the VOM or multi-meter to determine basic operational condition.
The stater solenoid is an electro-mechanical switch. The 12vdc from the ignition switch to the S terminal supplies power to the electrical coil of the solenoid and pulls the metal can (slug or plunger) into the solenoid housing to push a copper washer into two large contacts in the cap to supply 12vdc to the starter motor to make it spin. A check of the starter windings and commutator can be performed with an ohm meter (VOM) for open coils. The copper washer in the cap is a common failure point as it becomes pitted from normal operation.
The can (slug or plunger) in the electrical coil also pulls a bellcrank (lever) which drives the starter drive pinion (Bendix) into the flywheel. The starter drive is a ratcheting device that will freewheel upon the engine starting. The coil must compress a return spring around the can (slug) to pull the can (slug) into the coil and push the starter drive out.

The mechanical portion of the starter includes the ratcheting action of the drive pinion drive gear (Bendix) which can be affected by a weak or broken spring in the Bendix, worn teeth on the pinion gear, and the bronze bushing in the drive which guides it over the starter shaft and maintains alignment with the flywheel. There is a cupped washer, snap ring, and flat washer on the end of the shaft to prevent the drive pinion from hitting the starter nosing. The bellcrank pivot point and Bendix drive pads also are common wear points which can affect the stroke of the pinion drive gear.

The starter motor also has a bronze bushing at each end of the shaft of the armature. These bushings maintain the proper clearance between the armature and field coils and can affect the magnetic field between the two and thus the operation of the motor.

Then of course the flywheel ring gear has teeth to match the starter pinion gear and can be damaged by a weak actuation of the pinion drive gear due to weak electrical force, worn bushings, etc.

Hope this helps, if you don't fall asleep reading it.

 

Thank goodness for Christmas break! I was able to brave the cold and get out in the garage.

The wiring harness is about a year and a half old as I had to replace it last summer. I discovered there is a design problem with the connectors on the firewall for the engine harness the hard way. (There was the dreaded tow truck involved.)
I am getting good voltage every where.

Thank you guys for your input in this matter. I feel with what I have learned form you all and your experiences, I have a direction to head in. The teacher has become a student again.

I'm running with the thought it is a starter not aligned correctly.
My game plan is to drop the tranny and replace the ring gear. A lot of work for a $35 part! It will allow me to have a good look at the starter and be positive it is aligned correctly. I will also replace the pinion gear on the starter.

Then, while its out, I think I'll have the tranny gone through as I didn't do it when I restored the car some 10 plus years ago. Maybe replace the clutch and pilot bearing as long as it is all apart as well.

I get a buzzing in the shifter around 65 - 70 mph. I was thinking about replacing the shift linkage anyway thinking it was some excess play. But, I did see somewhere that it could be the driveshaft out of balance.

My list of things to do this winter is getting longer. I'm hoping for a mild winter here in northeast Ohio.