Our cars came with an external resistor, it's a resistance wire that runs between the ignition switch and ignition coil. As long as nobody has removed or bypassed the resistor wire you still have the external resistor. All cars with a 12 volt electrical system and running points in the distributor require the voltage to be reduced to the coil to prevent the points from quickly deteriorating. The coils that came on our cars required an external resistor, it just didn't state it on them.
This is why Mike recommended measuring the voltage to the coil, to make sure you do have the resistor.
Aftermarket electronic ignitions, that replace the points, may not require the resistor and reduced voltage.
One caveat, there are ignition coils available that have a built in ballast resistor. So, if you are running a point ignition you need an external resistor, either the one that was originally in the car or an add-on ballast resistor.