The HEI does not NEED 10 gauge wire. In conversations with Tom Langdon, the wire size was increased from a "normal size" due to an occasional miss during emissions testing, not because the ampacity of a 10 gauge wire was needed.
My wife's uncle was an engineer for the Motorola automotive products divsion and was on the team which developed the hei module. He says that it will fire down to ~4V. I have found the output to decrease proportionally with voltage and still be plenty at well below 12V. I have found the average current draw to be ~2 amps at 12V.
Just wire it up to a switched 12V supply.
