FF173k Wiring 1985

Hi,
New to forum in fact this is first time on any forum actually. I have a 1985 FF173k Hino we have had it over 10 yrs now. We pull a little 2.7 ton excavator around with it. Do cash jobs here and there. I had been having trouble with the wiring in the dash. I have had the dash apart and fixed a lot of melted wires that look like they had been like that a while. I have been trying to find some type of wire diagram of truck on internet with no luck there. Have been told by Hino dealers there is nothing out there. I'm diffidently not an auto elect by any means just after something guide me a bit more along the way. I purchased a manual on line and that does not cover wiring, rear split diff and pneumatic park brake. The manual not year specific at all but cover's ff, fd, and fe. Most things seem to match up though.
Could there be a better manual out there I can get?

Appreciate any feedback