What do you suggest as a way to view and count the flywheel teeth without removing the cover under the engine clutch bell housing?
And I guess I should also pull the s-plugs, etc?

Btw, I know that both previous and current pinions have 9 teeth. Although this latest armature with clutch drive has bigger and deeper pinion teeth.
It does not engage at all. When bench testing and moving the lever against the switch, it had full throw to the washer and bushing at the nose cone.
When I try the same thing in the truck (without battery) there is quite a bit of resistance in the lever and switch, suggesting that the clutch drive sheave is compressing its spring when trying to drive the pinion into the flywheel -- just not able to engage.

This truck had always been original 6 volt before I changed over just the basic electrics to 12 volt some years back.
The only major thing I changed was the generator to an alternator. Everything else has pretty much remained the same.
And it all worked well until recently.