Ignition experts needed

Just disconnect the Tach wire from your coil. This will surely tell you if it's the tach. The only reason I mentioned this is because my brother installed a Sun Super tach in his Duster when it was new in 1970. Evertime he pulled the emergency brake the car would die. I found that the dummy wrapped the wire from the tach to the coil around the E-Brake and when it was pulled it pinched the wire and caused the short.