Captain,
The Pertronix system has an operating range of 6 vdc to 16 vdc . Lower than 6 volts ,it WILL NOT FIRE, higher than 16 volts it WILL BURN OUT ! Measured at the coil terminals with the ignition key on " on "and all wires hooked up .
Now with the Pertronix system you will ONLY need an INTERNAL RESISTOR style coil . There is NO need to DOUBLE up on RESISTORS and POSSIBLY drop under the 6 volt lower limit . You mentioned that you are using a Pertronix coil, WHAT SIZE ,( 40 kv or 45 kv ) and what OHM rating and is it INTERNAL or EXTERNAL resistor type ?
You will also NEED to use a Mallory dist cap #221B and rotor #319 .That is the ONLY cap and rotor that WILL WORK ,TRUST ME on this one !
Now, if you ARE using the 40 kv or 45 kv coil ,you WILL burn out your plug wires in very short order ! You will need SPIRAL CORE ,LOW RESISTANCE (OHMS) to carry the increased output of the higher rated coil !