On a Ford style fender mount solinoid, there 2 small terminals. One is S for solinoid whick will activate the solinoid and get you cranking. The other should be "I" for ignition.That will get 12v when cranking . Run a wire from I to your coil and you should be good to go. Check it out w/ a test lite. There are MANY differant combinations for a Ford style solinoid, one of the small wires could go to ground.
If this is for raceing, dont run a resistor wire to drop volts when running, youll get a hotter spark this way.
Good Luck