Often, the most intimidating obstacle for many LS Swapers is the electrical system. However, there are many options when it comes to wiring your LS engine.
Many opt to leave the entire wiring harness from the donor vehicle, including the fuse box. The stock harness is left mostly in tact, thus reducing the chance for wiring errors. However, this option requires the relocation of the large fuse box with fuses for all of the donor vehicle systems. This isn’t the most aesthetically pleasing option, but it’s the most cost effective and simple solution.
Others choose to rebuild/rework the stock harness. All unnecessary wiring is removed from the stock harness, along with the factory fuse box. A smaller fuse panel is built, with the minimum number of fuses and relays to run the system. This option also allows the user to re-route the harness if the desired location for the fuse panel is not the same as the donor vehicle.
Of course, there are several manufacturers and individuals who offer stand alone harnesses to those who are willing to spend the money. These are often the cleanest options, but they can be expensive.