Electronic Ignition Conversion - 57 - 1 Per car

Regarding use of the original inline voltage dropping resistor:
If the coil measures 1.4 ohms or more the external resistor is not required.  However the resistor could be used anyway without a problem.
If the coil measures less than 1.4 ohms the external resistor is required.
Resistance is measured across the two terminal "BAT." and "DIST." with no wires on the terminals.

Install Directions