Wiring diagrams are in the assembly manuals, but if you just need a wiring diagram, Danchuk has you covered. The wiring diagram covers the complete chassis, overdrive, power windows and seats, air conditioning. directional signals, backup lights and neutral safety switch. You also get bulb specifications and the complete light switch circuit. Danchuk # 15572 covers the 1957 classic Chevy passenger cars only but information for the underdash and underhood wiring would be the same for Nomad and wagon.
Danchuk has the largest selection of quality 55, 56, 57 parts for your classic Chevy project.