LS3 Wiring Diagram - Pro-Touring I have a L76 crate with an LS3 top end (and a mild cam) that is going into a 69 firebird. Can someone help me out by providing this diagram? I pulled the following information off of the ECU. On the ECU, it says: GM Racing GM# 19258268 Gr. 3 LS SWAPS: Wiring Harness and Wiring Guide - LS Engine DIY LS SWAPS: Wiring Harness and Wiring Guide Includes in-depth instruction and photos. Covers all the criteria to consider when starting an LS swap project. it can be modified to greatly simplify the process of wiring the engine. The majority of the wires in the stock harness are not needed in a retrofit application. LS3 • Infinitybox This post is going to talk about how you connect your GM LS3 engine harness to your Infinitybox 10 or 20-Circuit wiring harnesses. Before you go anywhere, you must thoroughly read and understand the literature that came from General Motors about your LS3 engine and the wiring harness. WIRING DIAGRAMS Repair Guide - AutoZone The following wiring diagrams are provided to help troubleshoot electrical problems and as a an additional source to help understand the complex wiring utilized by these vehicles. No attempt has been made to illustrate most components as they physically appear, instead, representations are used to simplify the diagram.