Later cars have the ballast coil ignition , the 4th terminal on the starter solenoid, provides battery volts directly to the coil to give the spark more womph during cranking .. It is a threaded stud terminal but Ford provided only a push on connector.. The problem is getting a good connection out of this , a poor connection & it looses the same voltage as the ballast resistor.
I figure on bolting a ring connection , but will need to buy the nuts.. Anybody know what size/thread that stud is ?