[PDF] WIRING DIAGRAMS - 73-87ChevyTrucks. Classic Chevy WIRING HARNESS AND WIRES Every wire is a specific size with colored or striped insulation that is indicated on the wiring diagrams. Insulation colors help to trace circuits and to make proper connections. Abbreviations and symbols used for indicating wire insulation colors and patterns are as follows: Complete 73-87 Wiring Diagrams Here are the complete wiring harness schematics for the 73-87 series pickups. These are HUGE jpgs so you may want to save them to your hard drive and print the pages you need.