Working on a 2003 Chevy 3500 pickup, trying to replace rear tank fuel pump. The chevrolet factory pump comes with a newer style plug in and a wiring harness to wire in the new plug. The factory wiring that went to the old tank has two black wires the same diameter, a blue wire and a green wire. The harness has one purple one gray one black and one orange wire. Anyone know how to wire this?