I'm sure this has been dealt with before (sorry all) but although I can do most car wiring I have a mental block for electronic ignition. Dunno why... Anyway, my '72 240 has a Crane XR-700 module with a Pertronix 1.5 Ohm Flamethrower coil and a ballast resistor. IIRC this has an optical trigger which is inside a pretty stock dizzy. The tacho doesn't work. I'm wondering whether the tacho is sound but when the electronic ignition was fitted it somehow got left out. So... what wire do I connect to what to get it working and can I blow things up if I get it wrong?