The only function Pertronix performs is to short your coil to ground when spark should happen. Your points did exactly the same thing, but mechanically. Also, Pertronix uses no condenser.
Pertronix offers their own coils with different internal resistance called, 'Flame throwers', that should be used with a properly sized ballast resistor (if any at all). (Call Pertronix for ballast sizing.)
You can use your OEM coil and ballast resistor BUT make sure your Pertronix unit is fed with NON-resistor wire that comes from +12 volts (on the red wire to your distributor). - Dave