Photo of your 1969 coil?

[Rzeppa]

Ignition turned to accessory setting and get 12.59 volts to coil.

Ignition to Start and turn over engine and get 9.56 volts to the coil.

Is that enough voltage to the coil to do anything?

Generally, yes.

Could a 50 year old starter suck too much voltage?

Starters don't suck voltage, they draw current which can cause a voltage drop in the system depending on the resistance (V=I*R)

Could there be a voltage suck due to old/bad wiring connections?

There is no such thing as a voltage suck, however the voltage can drop during high current draw and higher than ideal resistance (see equation above, Ohm's law).

Could a 3 year old battery just not have the umph any more?

Yes, but not super-likely. More likely there may be resistance in the terminal connections and wiring (higher than ideal resistance).

 

[Rzeppa]

Oh it just occurred to me that a lot of people may not understand how that Ohm's law equation relates to this particular situation. V=I*R means that the original voltage will be reduced by the current being draw times the resistance of the circuit. So if the the measured voltage at the coil is 9.56 and it was originally 12.59, then the voltage drop is 12.59-9.56=3.03. So let's say the starter draws 10 amps, and Ohm's law says R=V/I, then you are looking at 3.03/10=0.303 Ohms of series resistance in the circuit between the battery and the starter. That's more than you want by around a factor of 3 or so, but it is still generally tolerable. Some of that is going to be in the battery itself. You can easily measure that by measuring directly on the battery terminals while cranking. The rest will be in the batter to terminal connection, the wiring to the starter, the connection to the starter, and of course the connection to ground.