GM Wouldn’t Approve the 1970 Buick GSX Until Two Secret Show Cars Proved It Deserved to Exist

A 1970 Buick GSX built and finished as one of Buick’s own factory show cars helped convince General Motors to greenlight the model at all. In this Muscle Car of the Week episode, owner Brad Conley walks through his Stage 1-equipped GSX at the 2018 Muscle Car and Corvette Nationals – a car with a documented pre-production identity shared by only a handful of surviving GSXs. See the full story, specs, and auction context inside.

Before General Motors would commit a single dollar to building the 1970 Buick GSX, it needed proof the public actually wanted one. So Buick pulled two identical white Gran Sport Stage 1 hardtops off the assembly line in early September 1969, dressed them up as show cars, and set them spinning on turntables at the 1970 Chicago Auto Show months before the GSX name ever reached a dealership. The gamble worked almost too well – crowds mobbed the display, and Buick greenlit a production run that would ultimately last only about ten weeks. Decades later, one surviving example connected to that pre-production story sat under the lights again, this time at the 2018 Muscle Car and Corvette Nationals (MCACN) in Chicago, where owner Brad Conley walked host Kevin Oeste of Muscle Car of the Week through a GSX built and finished as a factory display car rather than a standard production unit. It is a reminder that some of the most important muscle cars in history were never supposed to be for sale at all.

About the Video

This episode comes from Muscle Car of the Week’s long-running V8TV series – Episode 284, filmed on the show floor at MCACN 2018. Host Kevin Oeste tracks down owner Brad Conley for a personal walk-around of his 1970 Buick GSX, presented and identified as a prototype-spec show car finished with the Stage 1 package: an automatic transmission, console-mounted shifter, bucket seats, a 3.64 Positraction rear end, the Rallye Ride Control suspension package, G60-15 Goodyear Polyglas GT tires, chromed five-spoke wheels, tilt steering, power windows and locks, and the full Rallye instrumentation and steering wheel. Conley points out the details that separate this car from a garden-variety 1970 GSX – trim and finish touches applied specifically for a show-car build rather than a car destined for a dealer’s showroom.

What makes the segment worth watching is Conley’s own enthusiasm; he clearly understands exactly what he owns and why it matters to the wider hobby, and Oeste – who has hosted hundreds of these segments – treats this particular GSX as one of the highlights of the entire MCACN show. For anyone who has only ever seen a GSX in magazine photos, watching one in person, described in this kind of detail, closes the gap between spec sheet and steel.

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MCACN itself is worth knowing about if the name is unfamiliar. Held annually at the Donald E. Stephens Convention Center in Rosemont, Illinois, the weekend before Thanksgiving, the Muscle Car and Corvette Nationals fills roughly 400,000 square feet with more than 600 rare and historically significant muscle cars and Corvettes – a format built specifically around the kind of documented, story-driven cars that a factory show unit like this one represents, rather than a general car show open to anything with four wheels. It is the setting Muscle Car of the Week returns to year after year precisely because the ownership and history behind each car is as much the draw as the sheet metal.

From Show-Floor Gamble to Assembly Line

The GSX did not grow out of nowhere – it was the final, most extreme step in a Gran Sport lineage Buick had been building since 1965, when the Skylark Gran Sport first paired the intermediate Skylark body with the largest V8 GM’s rules would allow. That car sold well enough that Buick renamed the package GS 400 in 1967 and spun the Gran Sport off as its own model, before replacing the 400 cubic-inch engine with a new 455-cid V8 for 1970 and creating the GS 455. The GSX was positioned a full step above even the GS 455: an image-and-performance package built specifically to go after the Oldsmobile 442 W-30 and the Pontiac GTO Judge, the two cars everyone assumed Buick had no answer for.

The GSX almost did not happen on the 1970 production schedule at all. By the time Buick’s engineers wanted to introduce this fully dressed-out flagship, the model year was already underway and there was no time to validate demand through normal channels. Buick’s solution was to build two identical white 1970 GS Stage 1 hardtops, finish them to the still-unapproved GSX specification, and put them in front of the public at the 1970 Chicago Auto Show, held at the International Amphitheater from February 21 through March 1, 1970. The reaction from showgoers was strong enough that Buick moved ahead with production almost immediately, though the eventual factory GSX ended up differing slightly in detail from the two hand-finished show cars that sold the idea.

Because approval came so late, GSX production did not start until March 1970 and wrapped by May of that same year – roughly the back third of the model year. Only 678 GSX hardtops were built in total, split 491 in Saturn Yellow and 187 in Apollo White; of those, just 199 left the factory with a four-speed manual, while the remaining 479 were built with the automatic. Only 400 of the 678 were ordered with the Stage 1 engine package featured on this car. A GSX built and trimmed as a show car – rather than one of the 678 regular-production cars – sits in an even smaller category of survivors, which is exactly why a car like Conley’s draws a crowd at an event as serious as MCACN.

The GSX package itself was never subtle. For roughly $1,196 over a GS 455, buyers got a hood-mounted tachometer, front and rear spoilers, a blacked-out hood, GSX badging on the grille and instrument panel, and a full-length black body stripe outlined in red pinstripe running the length of the car and over the standard rear spoiler. Add the Stage 1 engine package on top of that, and the car pictured in this video represents about as complete a factory-performance statement as Buick was willing to build in 1970.

Under the hood, the Stage 1 package centered on Buick’s 455 cubic-inch V8, factory-rated at 360 horsepower at 4,600 rpm and 510 lb-ft of torque at 2,800 rpm, with 10.0:1 compression – up from 350 horsepower for a standard-engine GSX. Stage 1 cars added a recalibrated Rochester Quadrajet carburetor with revised jetting and air valve settings, heavier-duty valve springs, and a more aggressive camshaft profile. Buick’s own factory rating was conservative enough that period dyno testing reportedly showed real-world output running higher than the advertised 360 horsepower – a common practice across Detroit at the time, done partly to keep insurance underwriters from taking a closer look. On the strip, a 1970 GSX Stage 1 ran the quarter mile in 13.38 seconds at 105.5 mph in period testing, a number strong enough that Motor Trend named it the quickest American production muscle car of the year – a title that still gets repeated in muscle car circles more than five decades later.

What Makes It Special

Every 1970 Buick GSX is rare by modern standards – only 678 were ever built, and only 400 of those got the Stage 1 treatment shown here. But a car identified and preserved as one of the factory’s own pre-production show units adds a second, rarer layer on top of that: this is a piece of the story of how the GSX came to exist at all, not just an example of the finished product. That distinction is exactly why serious collectors and event organizers treat these cars differently, and why Brad Conley walking a national audience through his GSX at MCACN matters beyond just another nice restoration.

The GSX also arrived at a specific moment in muscle car history – 1970 is widely regarded as the peak of the era, the last model year before insurance surcharges, tightening emissions rules, and rising fuel costs began forcing every manufacturer to back away from big-inch performance. A GSX built to sell GM’s own decision-makers on greenlighting that peak-era performance car is, in a real sense, one of the cars responsible for the rest of the lineup existing in the first place – and a direct answer to the Olds and Pontiac flagships Buick was chasing when it built the car at all.

The collector market has caught up to that story in recent years. Regular-production 1970 GSX Stage 1 cars now average somewhere in the neighborhood of $133,000 at auction, with well-documented, numbers-matching examples pushing past $150,000 and a record sale reaching $236,500 in January 2025. A GSX carrying the kind of factory show-car pedigree Conley describes in this video sits outside that normal pricing conversation entirely – value here is tied less to a book number and more to the paper trail and the story, which is exactly what made this segment worth Muscle Car of the Week’s time at MCACN in the first place. It is also why owners like Conley tend to treat cars like this less as an investment to flip and more as a piece of Buick’s own history that happens to still run.

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