911 stranded, car has no spark

i have a 74 Duster. Car is running an MSD coil that is less than a year old. Already changed the ballast and ECM as I carry extras. Still no spark. It has been having an issue where sometimes it won't start when I first crank it and I have to turn the ignition switch all the way off then crank it again and it fires right up. Did try to see if it has spark using a screwdriver and sometimes it gives one spark when I release the ignition from starting to on. Please help! Thank you!

Jeremy