Mach 460 2003 requires Metra harness 70-5519.
The black plug provides high level signal for the tweeters and to the amps for the mids. The white plug (smaller) has 2 rca male ends that go to the sub out low level on the radio. The blue/white wires will go the a 5 volt remote turn on signal from the radio. You can build your own voltage divider using 2 resistors. One resistor about 500 ohms, and the other about 600 ohms. You want to grab your power from the 500 ohm resistor (5v).