Advice regarding a vintage kick down and a modern ignition
Your advice in Auto Restorer about disconnecting the ignition ground from the kick down may protect the Pertronix ignition, but the transmission will never kick down.
In order for the kick down function to work, you need a momentary torque interruption to allow the overdrive solenoid to pull the pawl out of the wheel on the planetary unit. Without ignition interruption it simply won’t kick down. There is a set of points inside the solenoid that provide the ground for the point ignition, momentarily killing the engine, until the spring in the solenoid pulls the pawl out and opens the points. The ignition interruption happens so quickly that you don’t notice.
Since you say that grounding the ground side of the coil momentarily will damage the ignition module, you would need to interrupt power to the module to achieve the torque interruption. This could be done by running power to the ignition module through a dual point relay using the normally closed set of points. You could then use the ground circuit through the kick down switch and overdrive solenoid to energize the relay; interrupting the power to the module and giving the torque relief needed to get a kick down into direct drive.
If you don’t do something like this, there is no need for the kick down switch since it won’t work.
Thank you for writing in. I think that your solution to the problem of getting a vintage overdrive electronic kick down to function alongside a modern electronic ignition module will work.