Ignition wiring

[Matt167]

ok, here's my dileima, I'm putting on a MSD 6 BTM box on my '67 Falcon, using a factory DSII distributor and a 8869 harness for the DSII- MSD connector ( plugs into the factory distributor plug ). that's the easy part. next part is, I need a 12v switched source, and I know my coil wire is my best bet, but it's a resistor wire, and when I checked it, produced 7.2V at idle ( I was having an intermittent problem with the bypass circut, so it wouldn't start, no need for a bypass ne more, so I'm not worried ), not enough for the MSD I don't belive. now, I know that I have to splice b4 the resistor wire, or run a new wire off the ign switch, but... which wire is it? I had every wiring diagram I needed ( even tho it was for a Mustang, Falcon and Mustang harnesses, are the same ) on my computer, but IDK where I put them. I kno I could go the easy way out and get a relay that will act on the low voltage, and wire it in that way but, that's cheap.