Re: coil question
There is a single wire coming out of the side of your distributor housing. Connect that wire to the negative side of the coil. The double wire goes to the positive side of the coil.
The double wire is comprised of two wires. One is from the outer terminal on the starter solenoid, and gives the + coil full battery voltage when your ignition key is in the "Start" position. The other wire piggybacked on the same terminal lug is the "ballast resistor wire" and it is energized when the ignition key is in the "run" position. Its function is to supply the + coil with 8/9ish volts at all times while the engine is running. Basically the resistor wire is a carbon core wire of a known resistance value. Much like your present day spark plug wires.
The breaker points will burn up quickly if they are run at 12 volts. The reason being that at 12 volts there is a pretty powerful spark at the point that the points open. Hence the "Ballast Resistor Wire" to step voltage down to an acceptable value.
Even with the "Ballast Resistor Wire" there is still a spark when the points open and absorbing that spark is the job of the "condenser" which is attached to the breaker plate inside your distributor. If you ever lose spark and everything looks perfect then you probably have a bad condenser. Those things have fooled many a mechanic.
When they fail they usually fail to ground and all of your ignition current is permanently grounded until you replace the pesky thing. They prevent that field collapse that gives you your powerful secondary spark voltage.
The telltale symptom of a bad condenser is when you put a test light on the negative side of the coil and crank your engine. If you get a steady light that means the current flow is NOT being interrupted any more by the breaker points opening and closing , rather its going straight to ground through the faulty condenser.
What Dean and others are calling a "trigger" wire (Black) is actually a ground wire which completes the electrical circuit from the ignition switch through the PRIMARY side of the coil to the breaker points. When the points are closed you are saturating the primary winding in your coil with electromagnetic flux.
At the instant that the breaker points open the flux lines collapse across the SECONDARY windings in the coil and induce the high voltage , low amperage current that fires across your spark plug gap.
The "Condenser" you refer to on the outside of the coil is wired to the negative side of the coil. Its there for RFI (Radio Frequency Interference)suppression.
If anyone is interested in seeing all of this stuff about coils feel free to acquire an old coil at the local junk yard and take it apart. Interesting stuff to be found inside. Did you know that they are full of oil? Yuppers. Helps em stay cool. Of course I am referring to stock GM type coils.
Sorry...didn't mean to rattle on but you know how I get late at night. Is the moon full?