Anmeter elimination

Any Chance anybody would be willing to help me locate the which wire I need to disconnect for the anmeter. I am going to use that wire ( I keep reading that it is yellow) to re route over to the negative side of my coil To hook up to my new tachometer. ( going to hook up to neg side of coil and then to my tach instead of anmeter).
I have never cut any of the wires but mine seem to be different for some reason. I have a Brown and red blue wire and then a large black wire going to my starting solenoid. the Brown wire is going to the "I" side and the red blue wire is going to the "s" side. On the positive side of the solenoid is the red battery cable, the large black wire and a yellow wire but both of those wires are separatelywith
connected with eyelets. The single yellow wire goes To what looks like some type of factory Junction right down by frame below battery like a rubber grommet almost. At the rubber style junction other wires go inside of it from the voltage regulator. Then 3 wires (one of them being a large black/yellow) go to a 3 wire plug, then those 3 wires go from the plug to the back of the alternator. Please help!!!