How to Swap an LS in a G-Body: The Complete Overview

1. Drivetrain & Engine Fitment

Getting the LS to sit correctly in the G-Body frame is the foundation of a successful swap. Proper driveline angles, firewall clearance, and crossmember alignment will save headaches later.

Recommended Components:

• ICT Billet LS Swap Engine Mount Kit – JEGS
• Hooker BlackHeart G-Body LS Engine Mounts – Holley
• UMI Performance LS Conversion Crossmember

Quick Tips:

• Match your transmission choice (4L60E, 4L80E, T56, etc.) before buying mounts.
• Use a low-profile oil pan (like Holley 302-2) for crossmember clearance.
• Verify engine centerline and driveline angle before welding or tightening mounts.

2. Fuel & Fuel Delivery

The LS demands consistent high-pressure fuel delivery (58–65 psi). Your carbureted G-Body’s fuel system will need a full EFI conversion.

Recommended Components:

• Holley Sniper EFI Fuel System Kits
• Aeromotive Phantom In-Tank Fuel System
• Summit Racing LS Swap Fuel Line Kit

Pro Tips:

• Replace all rubber lines with AN or PTFE hose rated for EFI pressure.
• Add a fuel pressure regulator near the engine (58 psi fixed).
• Consider a baffled or EFI-ready fuel tank to prevent starvation under acceleration.

3. Cooling System & HVAC Plumbing

Modern LS engines produce more heat than the stock 305 or 307. Upgrading your cooling system ensures reliability and drivability in any climate.

Recommended Components:

• Cold Case Radiators G-Body LS Radiator
• Griffin Performance LS Radiator Kit
• Mishimoto LS Swap Radiator

Pro Tips:

• Use dual electric fans with shroud for maximum efficiency.
• Integrate heater core hoses into the LS’s steam ports for proper bleeding.
• Keep the thermostat at 180°F for balanced performance and cooling.

4. Exhaust & Headers

Tight G-Body frame rails mean fitment is crucial. Choose LS-specific headers that provide clearance for steering and suspension components.

Recommended Components:

• Hooker BlackHeart G-Body LS Swap Headers – JEGS
• American Racing Headers G-Body LS Kit – Beefcake Racing
• CXRacing G-Body Twin-Turbo Headers – eBay

Pro Tips:

• Place O₂ sensors 10–12″ after the collector for accurate readings.
• Use heat wrap or ceramic coating to protect wiring and floor insulation.
• Opt for 2.5–3″ exhaust tubing with an X-pipe for ideal scavenging and tone.

5. Wiring, ECU & Controls

Electrical integration can be intimidating, but modern standalone harnesses make it easier than ever.

Recommended Components:

• Holley Terminator X LS Swap Kit
• Painless Performance LS Swap Harness
• BP Automotive Standalone LS Harnesses

Pro Tips:

• Use a dedicated ground strap between the block, frame, and battery.
• Disable VATS (Vehicle Anti-Theft System) in your ECU tune.
• Add a tach adapter if retaining the factory G-Body gauge cluster.

6. Accessories & Ancillaries

Power steering, alternator, and A/C setups require thoughtful packaging in the tight G-Body engine bay.

Recommended Components:

• Holley Mid-Mount Accessory Drive Kit
• Dirty Dingo LS Accessory Brackets
• Vintage Air Front Runner Systems

Pro Tips:

• Match power steering pump pressure (~1,200 psi) to your steering box.
• Custom A/C hoses will be needed — measure before crimping.
• Use shorter serpentine belts or low-mount alternators for hood clearance.

7. Final Integration & Tuning

After assembly, it’s time to bring your LS to life safely and correctly.

Checklist:

1. Check for leaks — fuel, coolant, and oil.
2. Prime the oil system before first startup.
3. Use HP Tuners or Holley EFI software for base tuning.
4. Monitor coolant temp and fuel trims during the first drive.
5. Retorque all mounts and headers after initial heat cycle.

Tuning Tip: A mild street tune — ~13° timing at idle and 14.7 AFR — gives smooth, reliable power while keeping temps under control.

8. Online Guides & Real-World Builds

Learning from others’ experiences saves time and frustration. These threads feature detailed walkthroughs and wiring diagrams:

• GBodyForum – “G-Body LS Swap” General Discussion
• LS1Tech – “The G-Body Swap Thread”
• LS1.com – “G-Body LS Swap Build Discussion”
• GBodyForum – 1983 El Camino 5.3 Swap Build Thread

Conclusion

The LS swap is more than an upgrade — it’s a rebirth for the G-Body platform. With careful planning, quality parts, and proper tuning, your classic can drive like a modern performance car without losing its vintage soul. Whether it’s a Monte, Regal, Cutlass, or El Camino, an LS swap delivers power, reliability, and that unmistakable 1980s attitude… reborn for today’s roads.