This is the usual Ford arrangement for the coil and ballast resistor.
The (+) is the power lead to the coil......and the (-) connects to the points in the distributor. the coil is switched on and off on the "down side".
There is a starting function where the coil is fed 12v directly from the starter solenoid. When the starter engages, the voltage really sags down - and you wouldn't want for it to be cut any further by the ballast resistor