How to Put a New Wiring Harness In an MGB | It Still Runs Putting a new wiring harness in an MGB was a consideration made by the car's company. Most of the wires on the harness will be fitted with the proper type connector for their use will also be the proper length and shape to reach their associated devices. 1978 mgb wiring | eBay Find great deals on eBay for 1978 mgb wiring. Shop with confidence. Skip to main content. eBay Logo: Practical 12V Autos Car Power Door Window Glass Lift Switch Wiring Harness Cable (Fits: 1978 MGB) Brand New. 1.0 out of 5 stars. 1 product rating - Practical 12V Autos Car Power Door Window Glass Lift Switch Wiring Harness Cable. $22.