I'd stay away from the Hayden 3647. I have two of them on the bench in my shop that have malfunctioning controllers out of the box. Both have the same issue; the 86 blade where the relay plugs in gets ~10.5 vdc when the yellow wire (ign on) is energized. The problem here is that the 86 blage is supposed to be the ground for the switch side of the relay!

I'm going to put in a call to Hayden to see if they will sort things out tomorrow. Stay tuned!