The Ultimate Guide to LS Motor Swaps in Classic GM Trucks

When it comes to breathing new life into a classic K5 Blazer or C10 truck, few upgrades compare to an LS engine swap. The LS platform has become the gold standard for power, reliability, and performance in the restomod world. Whether you’re working on a 1969–1972 K5 Blazer or GMC Jimmy, a 1967–1972 C/K Series C10, or a 1973–1987 C10 Square Body, an LS conversion transforms your classic GM truck into a modern-driving powerhouse — without sacrificing vintage style.

At Rust Belt Offroad, we’ve seen first-hand how the right LS setup can take these trucks from nostalgic weekend cruisers to daily-drivable machines capable of modern horsepower and highway comfort.

⚙️ Why LS Swaps Are So Popular

The GM LS engine family — first introduced in the late 1990s — is known for its lightweight aluminum design, compact size, and huge aftermarket support. Builders choose LS swaps because they combine modern fuel injection, reliability, and power with a design that fits easily into older GM engine bays.

Benefits include:

• Power & Performance: Factory LS engines range from 300 to 600+ horsepower.

• Fuel Efficiency: Modern EFI and ignition systems make them surprisingly economical.

• Aftermarket Support: Countless kits exist for mounts, wiring, exhaust, and tuning.

• Dependability: LS engines are known to run 200k+ miles with minimal maintenance.

🔩 LS Swaps in 1969–1972 K5 Blazer / GMC Jimmy

The 1969–1972 K5 Blazer and GMC Jimmy are icons of American off-roading, and their roomy engine bays make LS conversions fairly straightforward.

Key considerations:

• Motor Mounts: Use a swap kit designed for the 4WD Blazer frame — the engine sits higher than 2WD models.

• Oil Pan Clearance: Deep pans may interfere with the front crossmember; a low-profile swap pan is recommended.

• Transmission Compatibility: Many pair the LS with a 4L60E or 4L80E for smooth, overdrive cruising.

• Cooling & Accessories: Upgraded aluminum radiators, electric fans, and serpentine accessory drives keep the LS tidy and cool.

A properly installed LS transforms the Blazer into a reliable, powerful SUV capable of long-distance trips and off-road adventures — while maintaining that unmistakable classic look.

🚛 LS Swaps in 1967–1972 C10 and C/K Series Trucks

For 1967–1972 Chevy and GMC C10 trucks, the LS swap is one of the most popular upgrades in the classic truck world. These trucks combine vintage style with excellent drivability once modernized.

What to know:

• Frame & Crossmember Clearance: The C10’s perimeter frame provides plenty of room for LS engines. Use a bolt-in motor mount kit to simplify installation.

• Fuel System: Convert to a return-style EFI fuel system with a high-pressure pump and return line.

• Wiring Harness: Standalone LS harnesses are available with labeled connectors — making integration clean and reliable.

• Exhaust Routing: Headers and exhaust kits designed for LS C10 swaps will clear steering boxes and control arms.

For builders chasing both performance and originality, an LS-powered C10 can retain its classic charm while delivering modern throttle response and effortless cruising.

🛠️ LS Swaps in 1973–1987 C10 ‘Square Body’ Trucks

The Square Body era (1973–1987) represents the next evolution of GM’s legendary pickups — and perhaps the easiest platform for LS swaps thanks to their updated engine bay geometry and wider frames.

Things to consider:

• Mounting & Clearance: LS swap motor mounts bolt directly to the factory crossmember with minor modifications.

• Electronics: Many owners use a drive-by-cable throttle body to simplify wiring and pedal linkage.

• Fuel Injection Conversion: Square Bodies with carbureted tanks may need EFI-ready replacements or inline fuel pumps.

• Transmission Options: 4L60E, 4L80E, or even manual conversions like the T56 Magnum pair perfectly with LS power.

The result? A Square Body that starts instantly, idles smoothly, and makes power like a new Silverado — all while keeping that timeless boxy styling.

🔧 Common LS Engines Used in Swaps

• 5.3L LM7 / L33 / L59: Affordable and reliable truck engines — perfect for daily drivers.

• 6.0L LQ4 / LQ9: Strong low-end torque; a favorite for heavier K5s and 4x4 builds.

• 6.2L LS3 / L92 / L99: Modern powerplants with big horsepower potential for high-end builds.

• LSA / LS9 Supercharged: For those who want serious power under the hood.

🧰 How Rust Belt Offroad Can Help

At Rust Belt Offroad, we don’t just build reproduction bodies — we help customers plan and execute complete LS swap builds. From engine fitment and mount fabrication to cooling systems, firewall modifications, and wiring layout, we ensure your classic truck or Blazer is ready for modern performance.

Our 1969–1972 K5 Blazer / Jimmy, 1967–1972 C10, and 1973–1987 C10 Square Body reproduction bodies are designed with precision alignment, true firewall geometry, and OEM-style mounts, so installing an LS engine is easier and cleaner than ever.

We also offer:

• Firewall-back and full-cab assemblies engineered for proper engine clearance

• Smooth or single-bead firewall options for custom LS swaps

• Bed lining, paint, and mechanical services

• Facility tours in Canfield, Ohio — see where American craftsmanship meets modern innovation

🏁 Conclusion: Modern Power, Classic Style

Whether you’re building a weekend cruiser, a show-quality restomod, or an off-road beast, the LS swap is the perfect way to combine classic styling with modern reliability.

At Rust Belt Offroad, we make it easier than ever to pair the best reproduction truck bodies in the country with the most trusted engine platform in the industry.

Built better. Built here. Built to last.
That’s the Rust Belt Offroad way.