1964 Barracuda Stereo Wire

There should be a harness connecter for the factory radio which contains swtched power from the radio fuse and switched light power for the factory radio dial. That wire may not get used , depends on the type radio you bought.
If you need to add a power supply for the tuner memoryand clock in the new one.. get that from horn , dome lamp, anything that is fused and hot at all times XCEPT for the brake light circuit. Sure the brake light switch is close and handy but you dont want your sterio wiring to kill your brake lights and cause a collision.