There is no "earth" at coil for the instruments???? Are you sure that's an earth wire on the diagram and not the wire for the tacho on sports instruments?
I think you are confused as to what an earth is and does?
Earth wires are generally always the same colour in a harness, they all go to "earth" which will be a metal object that is in some way connected back to the neg battery terminal.
I still recommend a test light. I can't work on anything that's 12V without one.
I still don't know what's not working? If the handbrake light doesn't come on then it will most likely be the switch in the lever, not a wiring problem. Gauges not working is often the sender, unless they are all not working then you check in the dash wiring.
I think you could have issues with using a red motor in a WB as well. They are not up to the emissions level of WB.