I have a 1972 Buick Skylark and the harness connected to the factory radio were not compatible with anything on the market. I traced the wires and pretty much knew which wires went to where. I clipped the wires and installed my head unit and got nothing(alpine 7982 3 disc). I even installed a second deck( sony cd player) and got nothing. How do I go about hardwiring? What size wire? Fuse between?(deck has fuse on hot wire). straight from battery?