Your unit shouldn't hit on your shifter unless you made it longer. If it's a Pioneer, Sony or JVC, theres a pastel green wire you simply need to separatly ground that out. If it's a Sony, there should also be a pastel purple one, that you can simply cap it off. Theres a Scosche piece you can get at almost any place that sells car products. If theres not a Scosche dealer in your area, im sure they have one that is similiar. Ask them to look at it and it should look like
This That piece is of course for a deck that has front and rear (optional sub) pre-outs. If you bought a fold out unit without those your an idiot.