"6 volt" Delco-Remy coils were designed to work properly with a system voltage between about 4.5 (cold cranking) to around 7.5 during full charged battery operation at cruise speed, without a voltage control resistor.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!