[James]

Is the carbon button on the inside of the cap there? If it is missing, the spark will not reach the distributor rotor or spark plugs. This can cause the coil to burn itself into.

Just a side note and it might not be a problem. With the ignition on and with 12 volts feeding the distributor, measure the voltage between the distributor housing and the engine ground. Should be zero volts (if a voltage {any amount of voltage} is present it is not grounded). If the distributor housing is not grounded, no sparks. The ICM is grounded through the base plate to the vacuum advance plate and then the housing. Only apply a thin layer of heat sinking compound to the ICM base plate, nothing should be insulating the ICM base plate to ground. Then secure it to the distributor vacuum advance plate.

Another way this can be check by removing the cap (and all of the wire connectors connecting to the cap and set it aside on the bench or toolbox.) and place the meter on 200Ω scale, measure between the ICM base plate and to the vacuum advance plate, then to distributor housing, and to the engine. Should be less than .5Ω resistance (don't forget to short the leads together first to determine what leads resistance is and substract that from your measurements).

If everything check good, the the ICM is at fault. I don't know if the auto parts store can still check the ICM (with a ICM tester) like they used to do years ago. This might also be worth a try.