Did you look inside the MSD distributor to make sure the rotor tip is clean and the cap is clean with no oxidation on the brass tips. Are you using an MSD ignition with their distributor? You might think about changing distributor if you can. The intermittent spark is your problem. Also make sure the spacing is correct in the distributor between the pick up and the reluctor teeth which is about .008 on a Mopar distributor. A paper card is about .020, so no good, it must be non conductive metal, like brass.
