Ancor wire tracker
I have not used the Ancor unit, but the principle is the same as the one that is used in tel-com to ID wires in a bundle.
You "push a tone" from the tone generator into the wire you want to track. Then using the tone probe, use it''s tip to ID the wire with the tone on it. You hear a warbling tone coming from the probes speaker when the tip touches the wire with the tone on it.
They work pretty well. We use the Progressive model 701 kit in the IT Dept. I run. Costs about $100 and is the industry standard.
But if you have that much wire, and it is old, you may want to think about re-wiring the whole thing. That is what I ended up doing on my 25yo boat. Probably pulled over 500'' of wire out.