Electrical help needed

A good reason not to use those early Chrysler ignition systems. Anything that uses a ballast resistor is old tech and adds those issues. That includes older after-market ignitions like Pertronix Ignitor (original, not II, III), Crane Cams XR700, and such. The GM 8-pin HEI module + coil is a better choice to upgrade from a points system. It will trigger from a Mopar e-distributor. The ballast resistors are too low to measure resistance accurately, so better to measure voltages as you did. When steady running, with a ballast, you should see ~8 VDC at coil+ (rel to distributor case). When cranking, it should be the full 12.6 VDC battery voltage (key switch bypasses ballast). Of course with a modern ignition (no ballast), you should see close to alternator output (~14 VDC) at coil+ when running. My old Mopars have a relay providing IGN power, so no worries with drops across the key switch. I installed a relay/fuse box from a ~1999 Jeep (black box in Avatar).