Squirrel 361

I know it's an older post, but I have 15 2500HD that came with JUST power mirrors but not lighting. I added the tow mirrors with it and the power side works, just not the lights. I've seen alot of the mirrors have two plugs, the main and a 4 pin after for the light section, mine doesn't have the 4 pin one. I'm guessing they are all on the main plug. Is there a way for me to wire them to make them work?