I am putting a alpine head unit into my 79 nova 4 door. The wires that run into the stock AM radio are a yellow, black, and grey. Im tring to figure out which one is a constant power, which is a power to turn it on when the car turns on and which is a ground.... Also can I hook the dimmer up to the dimmer for my gauge cluster lights? because I do have a dimmer wire coming from my head unit. Also can you tell me which wire is the positive from the stock front speaker and which is the negative... dark green or light green?