Might w some jumper wires cut to the chase and jump 12V from the batt positive post or the alt batt stud directly to the "point" of the pentastar ECU connector AND to the (+) primary coil terminal either directly or thru the ballast(after you ohm it) and if you go direct wo a ballast only let run a few seconds or so. I'm assuming the ECU has a good ground w all the changing you've did. forget the ign sw & jump the starter at the relay. All that is needed is the dist pickup needs to trigger the ECU to ground the coil pri to collapse it (the pri field). Still no go? Got a spare dist to plug in & spin it by hand & see if that triggers a spark. All this will eliminate the wiring/ign sw & help pin it down to a particular component. EDIT Let everything get good and hot as that's when "something" will start to act up

Like these guys are saying check the bulkhead. I've read through this twice and it doesn't sound like you've done that. Visually inspect them. I replaced ignition switches, ballast resistor, had the dash in and out multiple times. then I checked the bulkhead and the was the source of the problems. It sounds EXACTLY like what you are explaining. these bulkheads are a major problem area with all mopars. Like I said, my car would run fun and everything, then it would randomly do that. Even when I'm driving around it will randomly do that. check it