Install of aftermarket fuel guage question

Below are the color codes of the wiring at the dash harness plug. It's for '70 but most likely the same. If you cut or remove the Dark Blue wire from the plug then you can connect it directly to an aftermarket fuel gauge (S terminal). I wouldn't tap off the existing gauge. All should be well assuming you've matched the aftermarket gauge to your sender. Course, you'll have to send 12v to the new gauge too. You can tap into the orange wire for lighting.

Dark Blue w/tracer = Ign-on, +12v
Dark Blue = Fuel sender
Violet = Temp Sender
Orange = Instrument Lights
Red = High Beam Indicator
Light Green = Left Turn Indicator
Tan = Right Turn Indicator
Black = Brake light (ground)
Gray = Oil Light (ground) or to sender