This 1970 Chevelle’s Backyard-Built Supercharged LSX Doubles What Chevrolet’s Own LS6 Ever Made

A 1970 Chevrolet Chevelle built by a shop called Backyard Specialties runs a supercharged Kong Performance LSX rated anywhere from 750 to 900 horsepower — nearly double the factory LS6’s 450. The build rides on a Speedtech Performance chassis engineered decades after the body ever left Chevrolet’s factory.

A 1970 Chevrolet Chevelle rolled out of a backyard build with a supercharged LSX engine under its hood, and the number on the build sheet dwarfs anything Chevrolet itself ever bolted into the car. The factory’s own LS6 454, the big-block legend that made the 1970 Chevelle SS famous, was rated at 450 horsepower from the showroom floor. This one isn’t a showroom car. It’s a hand-built pro-touring Chevelle from the shop known as Backyard Specialties, running a Speedtech Performance chassis underneath and a Kong Performance supercharged LSX up front, and depending on which number you believe, it’s producing somewhere between 750 and 900 horsepower. Either figure leaves the factory car in the dust.

The car comes from Autotopia LA, the YouTube channel run by Shawn that has built a following filming walkarounds and test drives of custom-built muscle cars across Southern California. This particular feature follows the familiar Autotopia LA format: a slow, detailed walkaround of the exterior and interior, followed by the owner or builder talking through what went into the car, and capped off with the supercharged LSX getting exercised on the street.

A Backyard Shop With a Professional-Grade Build

According to the video’s own description, the car was built by “Backyard Specialties” using Speedtech Performance components — a well-known name in the pro-touring world for subframes, suspension, and chassis systems designed to let a 1960s-70s body handle like a modern sports car. Pairing that chassis with a Kong Performance supercharged LSX, a modern GM small-block built for serious boost, is the signature move of the pro-touring movement: keep the muscle car’s shape and attitude, but swap everything underneath for parts that didn’t exist when the car was new.

⚑ Featured Gear

Start Car Conversations →

As an Amazon Associate I earn from qualifying purchases.

The power figure is where the story gets interesting. Autotopia LA’s own title calls the car a “900HP Supercharged” build, while the build’s spec rundown in the video description lists the Kong Performance LSX at 750 horsepower. Builders and YouTubers sometimes round up for a punchier headline, so take the top-end number with a grain of salt — but even the more conservative 750-horsepower figure is nearly double what Chevrolet’s own LS6 454 ever produced from the factory.

What the 1970 Chevelle SS Actually Came With

The 1970 Chevelle SS 454 is one of the most celebrated muscle cars of the era for a reason. Chevrolet offered two versions of the big-block 454 that year: the LS5, rated at 360 horsepower, and the range-topping LS6, officially rated at 450 horsepower and 500 lb-ft of torque — numbers that made it one of the most powerful muscle cars sold by any American manufacturer that year. The LS6 454 was never a common option; it added real money to the window sticker and most buyers who checked the box knew exactly what they were getting into. Original, documented LS6 Chevelles have become some of the most sought-after and expensive muscle cars on the collector market precisely because so few left the factory that way.

That’s the backdrop that makes a backyard-built, 750-to-900-horsepower Chevelle worth paying attention to. The body and proportions are unmistakably a 1970 Chevelle, the car most enthusiasts picture when someone says “SS 454.” But everything that makes it move, stop, and turn has been replaced with technology that simply didn’t exist in 1970 — a purpose-built aftermarket chassis instead of the factory frame, and a supercharged, fuel-injected LS-platform V8 instead of a carbureted big-block.

Why Pro-Touring Builds Keep Winning Over Collectors

Pro-touring restomods like this one occupy an odd and increasingly popular space in the muscle car world. They sacrifice the “all-original” credentials that matter so much to concours judges and vintage-correct collectors, but in exchange they get a car that can be driven hard on a modern road without the numb steering, drum brakes, and leaf-spring rear end that came standard in 1970. A Speedtech-based chassis typically brings independent-style geometry, upgraded brakes, and a stiffer structure — the kind of underpinnings that let a car with this much power actually put it down instead of just spinning the tires in a straight line.

The reaction in the comments on the original video leans heavily in the car’s favor, with longtime Autotopia LA viewers calling it one of the best-executed Chevelle restomods the channel has featured — praise for the fit and finish of the interior in particular, alongside the usual appreciation for the wheel and paint choices. For a channel that has posted hundreds of custom builds across years of content, that kind of reception says something about how clean this particular execution is. Several commenters also pushed back on a common assumption in the restomod world: that a car this polished had to have been commissioned by someone with deep pockets and handed off to a shop from start to finish. Viewers familiar with the build insisted this one was different — a car actually built, wrench-by-wrench, by the person showing it off, not just paid for.

The Case for Building Instead of Buying

There’s a quieter story here about who actually builds cars like this. Backyard Specialties isn’t a boutique restoration house with a waiting list and a seven-figure price tag — it’s the kind of shop name that signals exactly what it sounds like: enthusiasts building serious cars without a storefront or a marketing department. That distinction matters in a hobby where it’s easy to assume every high-end restomod rolled out of a shop with a showroom and a sales staff. Plenty of the best ones are still built by people who just happen to be very good at it, working out of a home garage on nights and weekends, sourcing parts from specialty suppliers like Speedtech Performance and Kong Performance rather than going through a turnkey builder.

That do-it-yourself ethos is part of why the pro-touring scene has grown the way it has over the last two decades. Unlike full restorations, which require tracking down period-correct parts and often cost more the closer a car gets to “as it left the factory,” a pro-touring build can start anywhere — a rough driver, a stripped shell, even a car with known rust — because almost nothing from the original drivetrain or chassis is going back in. What stays is the body, the glass, and the silhouette that made the car iconic in the first place. Everything bolted to it is fair game.

Why the 1970 Chevelle Specifically Keeps Getting Picked

Chevrolet’s Chevelle ran from 1964 through 1972 across three body generations, but the 1968–1972 “SS” generation — the one this build is based on — is the version most people picture when they hear the name. GM restyled the Chevelle for 1968 with longer, lower proportions and a more aggressive stance, and by 1970 the SS package had grown into one of the most credible performance packages in the General Motors lineup. That’s also the year Chevrolet finally let the 454 cubic-inch big-block into the Chevelle SS, after years of enthusiasts stuffing bigger engines into the car through dealer programs and aftermarket swaps because the factory wouldn’t do it themselves.

The LS6 454 that resulted is still treated as the high-water mark of the whole Chevelle SS line. Only a relatively small number of 1970 Chevelles left the factory with the LS6 box checked, and surviving, documented examples now command serious money at auction — enough that reproduction and “cloned” LS6 Chevelles have become their own well-known problem in the collector market, with buyers needing cowl tag and build-sheet documentation just to prove a car is the real thing. A body style with that much baggage and that much history is exactly the kind of canvas pro-touring builders gravitate toward: instant recognition, a built-in fan base, and a factory performance pedigree worth measuring the new build against.

Chassis and Engine: The Two Upgrades That Actually Matter

A supercharged engine is the headline, but the Speedtech Performance chassis underneath is arguably the more important upgrade for how the car actually drives. Factory muscle cars of this era, including the Chevelle, rode on a traditional perimeter frame with leaf springs out back and relatively soft, understeer-biased suspension geometry tuned more for a comfortable boulevard ride than hard cornering. Pro-touring chassis systems from companies like Speedtech are built specifically to correct that: stiffer structures, modern coilover suspension, better weight distribution, and brake packages sized to match the power being asked of them. Without an upgrade like that, a car producing anywhere near 750 to 900 horsepower on a factory-style chassis would be nearly undrivable outside of a straight line.

The Kong Performance supercharged LSX pairs a modern GM small-block architecture — descended from the LS-series engines that have replaced big-blocks in most serious restomods over the past twenty years — with forced induction built to handle the kind of boost levels that push output well past what any naturally aspirated factory engine from the muscle car era could touch, regardless of displacement.

A Modern Build Wearing a 56-Year-Old Body

Whether the real number on this particular Chevelle is 750 or 900 horsepower, the larger point holds either way: a car that started life with, at best, a 450-horsepower LS6 under the hood is now running a modern supercharged LSX that leaves the factory car’s output decisively behind, riding on a chassis engineered decades after the body itself was stamped out in 1970. It’s the pro-touring formula at its most literal — keep the icon’s shape and its name, and treat everything underneath as fair game for replacement.

Watch the full video above and let us know your thoughts in the comments.