9-10 volts with the engine running at the coil (+) terminal is about right. Don't be surprised if the next time you measure voltage "key on engine off" if you get full battery voltage. That happens if the engine stops with the points open. Resistors only reduce voltage if they're flowing current at the time the measurement is made. You need to rig a bypass wire to the coil input while the starter is turning. If you're using a stomp starter, install the stomp switch intended for 55-62 engines with the small bypass terminal on the side.
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!