I went through very same thing with my 71. After beating the shit out of myself for about 3 weeks I left my tack unhooked and it started right and ran great. If I toughed the tack wire to the coil it would die. I haven't looked for the short in the tack yet I just left it unhooked and it runs great. Have you tried to run a hot wire to your coil and bypass your ignition and leave everything else off the coil.
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