Home > LS-58x Harnesses
58x covers the latest GM V8s, also referred to as the Gen 4 engine. This includes LS3, LS7, LSA, LS9, and Vortec Truck variants.

When you purchase a 58x LSx harness from Speartech, the harness comes with all wiring to the engine and transmission and includes a check engine light, diagnostic connector (can be used with an OBD-2 scan tool for diagnostic purposes), fuel pump relay, throttle pedal harness, fuse block, wires for a computer controlled cooling fan relay, and labeled wires for easy hookup to the battery, ignition switch, and fuel pump. Labeled wires are also included for tach, speed, and brake switch functions where applicable.


These custom stand alone harnesses are built for full function, closed loop control, and designed for non-emissions use (no post-cat O2's, purge canister, or fuel tank evap interface).The standard length of our new harnesses are 3.5'. This length is measured from the back of the engine (where the harness forms a single trunk line), to the location of the ECM, and is typically designed for mounting the ECM inside the cabin area.


This setup and measurements work for most of our customers, but as always, we can make the harness to your specifications. Just give us a call.


All harnesses are covered in our latest high-tech, high-temp woven covering for a durable, show car look!


We can make a standalone swap harness for any GM LS-58x LSx variant. LS2, LS3, LS7, LSA, LS9, Vortec truck engines, and anything in between, including VVT & DOD engines - L99, L76, L92, etc.

Feel free to use whatever transmission you want. We can make your harness for use with any of the popular options including: 4L60E, 4L80E, 6L80, 6L90, T56, T56-Magnum, TR6060, etc.

All ready have a factory LS-58x harness for your project? No problem! We offer factory wiring harness reworks to get your project up and running easy. Just go here for more info.

We created a helpful guide to assist you in selecting the proper options when ordering a harness. It's a great reference point for you to find out what you are using with your project. It can be viewed here: LS-58x Harness Options Info


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