Ammeter Bypass=NO SPARK????

Ignition switch bypasses the ballast during starting, if not, no spark.
Engine that starts but dies after key is released has no circuit through ballast resistor circuit.
At that point (1963) Chrysler had just introduced solid state radios using germanium transistors, and earlier ign switches did not remove all accesory power during starting.
When removing the cranking power from the starter, there would be a large inductive kick back into the 12v, and the brief spike in voltage would take out radio transistors.
Germanium transistors have a much lower turn-on potential than silicon, .3 volts vs .7 volts. They "punch through" and short with very little abuse.
This is why the radio is off during cranking.
Earlier tube radios did not have this problem.
The ignition switches were re-designed to correct this issue.