Amp Power Source

Well you guys are speculating, helpful as you are trying to be. If this uses a dedicated "big" wire feed similar to MSD, with a smaller "trigger" wire, there is no need for an extra relay, certainly not a big solenoid. Just run the trigger to a keyed source. Not sure? Easy. Measure the current draw on the small "power on" wire. If it's less than an amp, just wire it through the fuse panel as you would a tach, etc.

The size of the "power on" wire should be a big clue.