No spark on my 84 Ram.

johnnymac2k6 said
Swap out the mag pickup in the distributor with a new one, or the one from your dart. These can come and go, and play all kinds of intermittent spark issues. I chased your exact issue for a year, and after hundreds of dollars worth of ignition boxes and coils, it was the $16 mag pick-up, deciding to work when it felt like it.
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+1 This issue had me chasing my tail for like 2 months on my duster when it was a/. With my 360 I was having starting issues and the tack was really erratic and eng missed at above 4000 and ended up being the screws that hold ign module on had stripped creating a bad ground.