Go here: http://firstgens.com/home.html
You'll need to register, then you can log in and download wiring diagrams via the "download documents" link at the top.
Alternatively, you can buy reprints of the original factory wiring diagrams from parts vendors, and online via eBay, Amazon, etc. Cost about $5 last time I bought one, well worth getting one.
1969 04A Van Nuys-built Z/28. Cortez Silver with dark blue interior and VE3. Sold Clippinger Chevrolet. Raced at Lions in LA.