While we're on the subject of older Dodge/Mopar ignition circuits, a quick lesson, starting with the spark plugs and working backwards ...
Spark plugs require a very high voltage to 'do their thing.' Per Wikipedia:
Spark plugs usually require voltage of 12,000–25,000 volts or more to "fire" properly, although it can go up to 45,000 volts.
The higher the voltage, the 'hotter' the spark. The spark plug gap has a bearing on how much voltage is needed, with wider gaps requiring higher voltage.
The distributor send the high voltage to the right spark plug, when the plug is supposed to fire. Older distributors used a set of contacts (points) to cause each plug to fire at the correct instant, relative to the piston's position in the cylinder. Newer (electronic) distributors use an electromagnetic sensor (reluctor) to determine when to 'shoot' the current to each plug.
In both types of distributors, the 'gap' for the points or reluctor is critical. In points-type distributors, steel feeler gauges could be used to set the gap. Because of the magnet in reluctor-type distributors, brass feeler gauges are vital to accurately set the gap. (An advantage for electronic distributors is the reluctor rarely, if ever, needs to be re-gapped, unless the reluctor needs to be replaced, slips due to loose screws, or someone messing with it.)
Electronic ignition Dodge ICMs use the 'signal' from the reluctor to 'know' when to trigger the high voltage current.
The ignition coil is essentially a 'step-up' transformer. It converts the relatively low (roughly 13.5 volts) input voltage into the thousands of volts needed to fire the plugs.
The plasma created by the high voltage spark tends to 'blast' material off the spark plug electrodes. The 'hotter' the spark, the more material is 'burned off.' (This is why spark plugs need to be re-gapped or replaced periodically.)
Cold engines need a relatively hotter spark in order to start running. Once the engine is running, a 'less hot' spark is suitable for continuing operation. So, an ignition circuit needs to 'switch' between a 'hot' spark and a 'not-so-hot' spark, mostly to extend the time between re-gapping/replacing spark plugs. (Lots of stop-and-go driving, versus longer trips, tends to wear out spark plugs faster.)
This dichotomy is the reason for the ballast resistors in Dodge ignition systems. The ballast resistor reduces the voltage going to the ignition system, resulting in a 'not-so-hot' spark.
When I was trying to come up with an example using actual numbers, I wound up going down a rabbit hole of algebra, physics, and mathematical calculations. Assuming my starting figures are correct and I didn't screw something up somewhere, 13.5 volts input to a 5 ohm ballast resistor yields a 10.8 volts output.
The START circuit in our older Dodges bypasses the ballast resistor, supplying a full 13.5 volts to the ignition circuit. (This is for a two connector ballast resistor, the START side of four connector resistors is low resistance so essentially the same.) The RUN circuit goes through the ballast resistor, supplying 10.8 volts to the ignition circuit.
Assuming a 25,000 volt output from the coil during starting (and a simple ratio relationship), the output from the coil while running is 20,000 volts. (25,000 divided by 13.5 times 10.8)
I'll take a break while everyone goes get some aspirin or a stiff drink.
