I'm having the same exact problem with my '71 Duster. I have checked nearly everything. Changed distributor, cap, rotor. Switched spark plugs and cables around to no avail. I even did a compression check. All is well. The last thing I checked that got my attention was the voltage output of my alternator. Turns out that it is going from 12.3 at idle to over 16 volts. Tells me that the voltage regulator is shot. I am assuming that the ecu is shot now because of overcharging. I still need to get a regulator and then test everything again.
