Use a ballast resistor specified for any GM vehicle produced from about 1955 to the late 1960's. They're all the same. According to Rock Auto, you need a Delco U505 coil and a Standard Motor Products RU10T resistor. The RU10 will also work, but the T series has connectors that resemble the original equipment part if that matters to you.
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!