LS Swapping a 1973-87 GM Square Body Truck (photos)
Many consider the classic 1973 to 1987 GM square body pickups to be the new gold standard when it comes to muscle trucks. Numerous companies now offer upgrade parts to combine modern performance with the classic body lines and make an affordable hot rod that can be daily driven. Because of the abundance of these trucks produced, they are a perfect platform for an LS-based engine swap.
1. Kits & Components
The third generation GM/Chevrolet C/K trucks have a ton of room under the hood, seeing as how they were offered with factory big block power, making them one of the easier platforms capable of accepting LS power. Although many companies originally produced LS swap kits for cars only, a number have jumped on the bandwagon to offer complete kits made specifically for the square body GM trucks, including Holley/Hooker and BRP Hot Rods/Muscle Rods. There are also a number of aftermarket companies out there offering other parts with some neat features if you are interested in piecing it together yourself. All in all, an LS powerplant is a near perfect fit in the C/K chassis and clears original equipment such as the brake booster and steering shaft.
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2. Engine & Transmission Mounts
Once you've acquired your engine, you"ll need to nab a set of LS-specific engine mounts to make installation a breeze. While many brackets come in fixed positions, some companies like Dirty Dingo Motorsports offer adjustable brackets that allow for up to 3" of fore and aft adjustability for accessory-drive fitting or weight distribution. As far as transmission crossmembers go, just about any transmission can be used with an LS in the C/K truck including the Tremec T-56 6-speed, TH350 & TH400, 200-4R, 700R4, TR6060, 4L60E-4L75E, 4L80E-4L85E, and 6L80E-6L90E. Adapter bracket, mounts, and crossmembers typically come with polyurethane bushings and hardware necessary too. When ordering a kit from somewhere like LSX Everything, simply select your transmission option from the menu to ensure you receive the correct parts.
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3. Exhaust
An exhaust system for your LS swap has never been easier with the exhaust offerings from the Holley/Hooker LS swap catalog. You can use block hugger style cast iron manifolds, or long tube headers, with 1-3/4" or 1-7/8" primaries, and 3" collectors. The full stainless x-pipe exhaust system can be had in either 2-1/2" or 3" and is designed to work with the stock ride height, but also works with dropped trucks lowered 5"/7". Additionally, they offer a standard rear-exit system or a side-exit setup that ends just aft of the rear tires. I you aren't looking for a full bolt-on setup, you can purchase various sized Muscle Rod headers and fabricate the exhaust at your local muffler shop.
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4. Cooling & Fuel System
When swapping in a LS motor with extra ponies, you are going to need to keep it running cool with a performance radiator. Kit manufacturers like Holley and BRP offer their own LS specific radiators as part of their kits. LS swap radiators specific to the 73-87 trucks can also be had from specialists such as Griffin Thermal Products that will drop right in.
With the C/K line of trucks being carbureted, the fuel system will have to be upgraded in order to run fuel injection (or you can convert the LS motor to a carb set up). BRP offers a complete fuel system setup that provides a new baffled fuel tank, in-tank fuel pump/sending unit, regulator, fuel lines, and all necessary gaskets and hardware to fit nicely into the truck. You can also use the tank and sending unit from the 1987 fuel injected truck by upgrading the in tank pump to one that can put out the needed pressure.
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5. Oil Pan & Accesory Drive
Oil pan clearance is typically an issue on LS swaps, but rest assured, high clearance oil pans are available that will fit flush to eliminate any interference with the chassis/mounts. Similar to oil pan fitment, accessory drive setups often have clearance issues. For the square body LS swap, the modern truck/SUV style accessory drive configuration is ideal, because it will drop right into these older pickups with only minor clearancing needed on the front edge of the new passenger frame bracket for the AC compressor (if using AC). That said, there is room to move the AC compressor onto the top of the engine opposite the alternator with an adapter bracket.
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6. Wiring & ECM
Wiring harnesses, fuse boxes, and replacement ECMs can be a pain on LS swaps, but swap kit manufacturers and companies like Painless Performance, Speartech, and PSI, make it pretty straightforward. These aftermarket harnesses are designed specifically for LS conversions,and eliminate all unnecessary plugs and circuits and their re-flashed ECM gets rid of anti-theft detection, post-cat O2 sensors, etc. For the most part, you only need to specify which LS engine you a using, as well as transmission, and your wiring harness/ECM/fuse box will arrive ready to rock and roll.
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For help with keeping your LS powered car or truck running right, check out the how to section of LS1Tech.com