an electrical nightmare , please help , 1972 dart

Rotor "punch through." This is almost always caused "by lightning" so to speak. Coil output voltage is VARIABLE depending on the LOAD. You have the coil, the coil wire, the rotor/ cap, the plug wires (and connections), the plug--and maybe resistor plug or "booster gap" plug OR IT MAY BE BROKEN or GAPPED really wide, and then you have the CONDITIONS inside the cylinder.

When something like a bad plug wire, burned valve, etc cause the coil to BECOME UNLOADED at that cylinder, the COIL VOLTAGE goes way UP. Just like lightning, it looks for a place to jump. If the rotor is poor material, cracked, heat damaged, dirty/ moist etc spark can generate a path and heat that up until it CARBON TRACKS and then it is all out drills a hole right through.