After almost 5 years, I recently replaced the battery on my '46 1-1/2 ton. Your symptoms sould like mine before I got the new battery. A battery that does not produce sufficient cranking amperage will turn the starter motor furtively and slowly--once, twice, or maybe three times, then stop turning, not recover, or make one more partial turn before giving up.
The situation is not good for a lot of electrical things inside the starting and electrical system. Voltage drops low, current (amps) continues to flow, but at such a reduced rate that nothing is working right, and most of the current is just used to produce heat in the wiring, components (coil, distributor, generator, starter motor, and regulator) and battery.
I have a 6 volt original electrical system. The battery is a wet cell with access plugs, that is, the three holes in the top of the battery you can open to add water and look inside (sort of).
Once these batteries start to get weak and not hold a full charge, you end up with a "top charge" or partial charge, which is insufficient to provide enough amperage to crank the starter motor one or two turns. Hence, the battery appears to go "dead" when you try to start the engine, and it won't recover.
This will always happen when the air temperature is 106 degrees fahrenheit, or 23 degrees below zero. That way you will be the most uncomfortable whe you have to remove the mats and floorboard to change the battery.
Lights and horn may work up until you drain the charge by trying to start the engine, but even the other electrical things will act weak and lifeless.
Solution, new battery.
I spent $80 on the battery, a new cable from the battery to the starter motor connection post and a new ground strap from the battery to the bolt on top of the tranny case.
Now, when I mash the starter, the starter motor spins at full speed, the engine fires after one revolution at most, and then slows down to idle speed. That's the way it should be.
