Per the edelbrock book, mount the ground directly back to the choke housing. As for the power, they specifically mention not to tap into the coil post. Mercruiser uses the AC tap on the back of the alt for their electric chokes. I used this as well and it perfect. Its not a keyed 12v source but its a source ONLY when the motor is running. This way you dont have to worry about a dead battery in case you turn the key for something and forget.