It might be tough to do, but if you can identify one end of the wire (such as the ammeter connection end,) you could use a multimeter (or powered test light) to "ring out" the opposite end of that wire. Clip one meter probe on the known end, and then touch every other wire with the other probe. When you get the beep (or light), you'll know that's the other end of the same wire.
If you have specific spots you can't ID, list them, and maybe someone with an original wiring diagram can help you figure it out.
