LS Swap Guide for Chevy & GMC Trucks

The LS swap is the most popular engine swap in history, and full-size GM trucks are the easiest place to do one. This hub organizes the FSC LS content by what you’re actually trying to figure out — how the engines and electronics differ, how to identify a donor, cost, kits, engine choice, wiring, mechanical systems, and buying a used LS — so you’re not piecing it together across a dozen posts. For platform-specific buying and build notes, see the Squarebody, OBS/GMT400, GMT800, and GMT900 hubs.

Latest LS Swap Content

Start here

• Gen III vs Gen IV LS Swap Guide — the engines, electronics, controllers and what’s actually compatible
• How to identify an LS donor before you buy — RPO, VIN, crank/cam signal, throttle, controller
• LS Swap Guide for Chevy & GMC Trucks — the big-picture overview
• LS Swap into a Full-Size Chevy/GMC — complete guide thread (forum)

Choosing the engine

• Best LS Engine by Goal — budget, towing, power, simplest wiring, lightest, or six-speed

What it costs

• LS Swap Cost: How to Build a Real Budget

Kits & parts

• The No-BS LS Swap Kit Guide

Mechanical systems

• Oil pan guide — choose the pan by your chassis and 2WD/4WD, not a “front-sump” label
• Accessory drive guide — truck vs Corvette vs F-body spacing and clearance

Wiring

• OBS Chevy LS Swap Wiring Harness Guide

Buying a used LS

• LS Engine for Sale: The No-BS Buyer’s Guide
• Used LS3: What to Check Before You Buy

Owner tools for your swap

Free, no sign-up. The decoder in particular earns its keep when you are identifying a donor.

• GM RPO Decoder — if the donor is still a complete vehicle, photograph the SPID label and decode it before you hand over money. The RPO is the engine’s real name, and it beats a seller’s description or a valve cover every time.
• GM RPO Code Database — every option code we hold, searchable by code or by plain description, and filterable to model year. Useful for pinning down the donor’s transmission and axle as well as the engine.
• MPG Calculator — miles, gallons, engine. Worth a baseline before and after a swap.

Still on the bench: a tire, gear and speedometer calculator for working out how far off your speedo reads after a size change and what it did to your effective gearing, and quick identifiers for engine RPO, axle code, transfer case and AFM/DFM — the things you need standing at a parts counter.

See all FullSizeChevy owner tools →

Show your swap

Post your LS-swapped build in the FullSizeChevy forum →