Detailed chassis wiring manuals are costly. Forty years ago I paid three hundred dollars for (3) Mitchell manuals. From a quick glance, I gather they changed formats. Online only and subscriber only (monthly).
The best information (by far) is direct from the chassis manufacturer. GOOGLE FACTORY CHASSIS WIRING MANUAL with your information. The same applies to Technical Service Bulletins related to wiring and everything else.
Don't expect this to be cheap. But in perspective, hourly service labor rates should be considered.
