Squarebody LS Swap Guide | 73-87 C10 Parts List

When you combine the most popular truck of all time with the most popular engine of all time, you end up with a glorious combination. LS-swapping a classic Squarebody C10 is the best way to maximize power and drivability from a beloved era of trucks and SUVs.

While most of the process is fairly simple, there are some tough issues that you will face. Luckily, the aftermarket has risen to the challenge of helping you get your Squarebody C10 LS-swapped without too many headaches. If you want Chevy Square body C10 LS swaps explained, continue to read on!

If you want a reliable, affordable engine that will swap into your truck easily, the 5.3l LS is the best because it hits all those marks. You can easily get 200k miles out of a 5.3L LS without even looking at it, 300k+ if you take care of it. Under 200k, you can often rebuild them with a basic ring and bearing kit without needing machine work (always check clearances and cylinder bores first!) and get another 200k out of it. That’s why the LS engine is so popular, across the board, these engines simply last longer than the Gen I SBC. Plus, you can easily get 600-700hp with a little boost and not have to change the rotating assembly.

Want bottom end grunt without hassling with turbos? The 6.0L Vortec LS-series engines are built for it. If you can afford to spend on a 6.2L L94, L9H, or L92, you can get even more power naturally aspirated (no boost), and you can boost them to ridiculous levels if you want to.

The better answer for this question is reserved for crate engines, as you can buy a fresh 5.3L LS crate motor from Speedway for a touch over $5k and get 475hp and 435 lb.-ft of torque shipped to your doorstep.

Your LS engine of choice doesn’t really matter much in terms of the swap components, as most of the parts you need are fairly universal in regard to the engine itself. Performance components, wiring harness and ECM, and exhaust manifolds/headers do matter, as some things changed between generations of LS (Gen III vs. Gen IV), year, and engine version. It is best to know what engine you are swapping BEFORE you buy parts, that way you get the parts you need and don’t have to go through the process of returns and exchanges.

Pro-Tip: The V6 frame mounts DO NOT work with any LS motor mount adapters, unless specifically made for the V6 stands. All of the mounts mentioned in this article require the V8 frame stands.

The transmission of choice dictates this position in most cases. Keeping the original bellhousing plane position allows you to keep the original transmission and drivetrain components, which if your truck or SUV had a 700R4 auto, also translates to the 4LXX and 6LXX series of overdrive autos. Most swappers opt for a newer transmission, so this changes the game. If you are going with a new 8-speed or T56 manual, the more forward position of the engine is beneficial as it yields a little more clearance for the transmission in the tunnel.

For this era of truck and SUV, it is highly recommended that you do not reuse the original driveshaft. The older technology used for these driveshafts is not up to task of holding up to the higher horsepower of an LS engine, and long-wheel base versions used two-piece shafts, which are better off replaced with a single piece unit. Speedway Motors offers new quality assembled and balanced ready to drop driveshafts that are built to your specifications that you provide at the time of the order. These driveshafts come in either Steel, Aluminum, or even Chromoly.

Once you have the motor mounts selected, you may need a new transmission crossmember depending on your trans choice. If you go for a 4LXX or 6LXX, then this crossmember will do the job with the above linked ICT Billet motor mounts. This unit also fits 700R4, 2004R, Th400, powerglide, TH350, Muncie 4-speeds, T10, TKO, and T56 transmissions.

In most cases, your driveline angle should match up to the original with these adapters and crossmember, but always check the fit in the vehicle. The target is 2-degrees down for the transmission and 2-degrees up for the rear pinion yoke. The usable range is 1-5 degrees for maximum U-joint life and vibration-free driving.

The best stock oil pan for a 73-87 C10 LS swap is the LH8 or “Hummer” pan, this is the exact same pan that GM rebranded as the “Muscle Car” oil pan, check out the FiTech 82-87 GM Truck 58015 EFI Fuel Tank. This pan will hang below the front crossmember about a half-inch in most installs, which is suitable. The other stock pan that fits the 73-87 C10 LS swap is the 98-02 F-body pan.

Outside of those two stock pans, there are serious fitment issues with the others, pushing you to the aftermarket. The Chevrolet Performance LS swap Muscle Car pan is good, but the Holley oil pans are a bit shallower on the main sump, so you get better chassis clearance.

If you want headers, a good solution is a the Hedman Hedders 69710 mid-length header, which is best for lowered vehicles where ground clearance is an issue. If you want full-length headers, have a look at Doug’s Headers 447D314, which are ceramic coated and provide that full-length exhaust experience so many crave.

If you need to test fit headers before your engine is ready, we recommend using our LS engine mockup block and LS swap mockup heads to get started.

From there, the rest of the exhaust is easy, just about any C10 exhaust kit that fits your vehicle (wheelbase matters here!) should handle the business of getting the stinky stuff out of the engine. For a naturally aspirated 5.3L, a 2.5” dual exhaust is about perfect, 6.0s should get 2.5 or 3” duals, while boost requires a custom or Universal exhaust kit to get the job done.

You can stick with a mechanical fan for your Chevy Squarebody LS swap, which requires a Gen III Vortec water pump in most applications, but you need a fan shroud and new fan clutch should you opt for this. In most cases, you might want the extra room afforded by electric fans, which deliver better cooling and help your engine get up to temp faster than a mechanical fan.

The best option, however, is to simply go for a drop-in fuel pump module or replace the crusty old fuel tank entirely with a new tank that is designed for C10 LS swaps. This FiTech tank is not cheap at a little over $600, but you get a new fuel pump and sending unit as well, which if you add these up individually, is bargain. The old tank is absolutely full of rust and varnish, the level sender is almost guaranteed to be inaccurate if not dead entirely, and again- new in-tank pump. It is worth the cost of entry.

Unless you are building a mega-horsepower engine, the stock ECM is actually the BEST option for any LS swap plan. GM spent mega-millions developing the software and hardware for these engines, the aftermarket controllers do not have the same reliability, so unless you just have to have it, the stock ECM is actually much better. Oh, and as a side note, the stock ECMs have built-in controls for GM 4LXX transmissions, so you don’t need a separate TCM.

That does come with a caveat, the stock ECM requires a tuner, but don’t get scared by that. You need to delete the VATS system and some trouble codes for your engine to run properly. There are many locals that will do this for you for a small fee, and some harnesses even come with a mail-in exchange program. Once it is unlocked, outside of performance tunes, you don’t ever have to get back into the ECM software

For a budget accessory drive, Bills Hot Rod Co offers an excellent LS Accessory Drive Kit for just under $1200 that includes a new alternator, AC compressor, water pump, power steering pump, and all the brackets and pulleys. Want to go all in with a super-sleek accessory drive? Then the Vintage Air Front Runner is a great option, with all new components, polished ARP hardware, all coated in a killer black anodized coating for long-lasting good looks.