Point of order: The R terminal on the starter only supplies 12V to coil during cranking (key at "Start" position), then when motor starts, and you let go of the key, the key returns to "ON" position. Then the resistance wire carries the voltage to coil (8-9V). You have said that when you tested the coil with ignition "ON" is was 11.94V. This says something is wrong. Unless you didn't test it correctly as I described. I'll give you the benefit of doubt.

The yellow wire is supposed to be from starter "R" to coil pos. The resistance wire is supposed to come from the ignition switch "ON" terminal. So now I want to know what the voltage is at coil positive with motor cranking. You may need a helper for that. Do that test ASAP.

The fact that there is 11.9/12V with ignition "ON" is OK now that you have Pertronix, but not OK for the points. I just want to make sure there is 12V with key at start/motor cranking. Motor will have weak spark if coil is only getting 8-9V while cranking and Pertronix only getting 8-9V during cranking............or maybe voltage is zero during crank. A low battery or a battery that breaks down will contribute to this or cause all this. I don't pay any attention to posters who say this or that is new. "NEW" has it's own dangers. Lots of bad parts now-a-days and inexperienced installers/owners who damage parts right away. It would be normal for a battery to be low after many tries of starting without recharge however.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn