With the points closed, there should be no measureable voltage at the (-) side of the coil. It sounds like the circuit through the points is not getting completed for some reason, either incorrect connections inside the distributor, or the distributor housing failing to get a ground. Points open- - -battery voltage at the coil (-), points closed, 0 V. at the coil (-) terminal. If it's not doing that, the coil can't develop a spark.
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!