relay powered voltage regulator ?

I'm looking at doing this same mod on my 73 Duster after talking to Mark from MAD electrical, too. I've already done the alternator bypass and I just finished running my headlight relays. He actually sent me a diagram of how to install the relay, but I'm still kind of confused as to what wire I'm supposed to use for "Ignition Feed" (85 terminal). Is there a specific wire to splice into for this? Also, just to clarify the 87 terminal just get spliced into the blue VR wire, right? I recently replaced the pigtail on my VR, so I was just going to cut into that splice.