Ok that makes a lot of sense. I think I'll buy the electric and hook the positive up the ballast and then the negative to the engine block or carb for ground.
This is the first I have worked with a carb before and surprised and how much time I am spending with it. I am not familiar with the carburetor solenoid. A quick google isn't turning up much on it. Maybe it also goes by a different name? Is this more of a option or a must have for the car to run correct.
I suggest you find a keyed 12v source and NOT use the ballast circuit , the voltage on the coil side of the ballast is less than 12v and the choke wants a 12v source. Many people connect it to the coil because they are too lazy to find a proper source.