The '60s was the golden era of muscle cars, with high-performance models coming fromFord, GM as well as Chrysler at the time. Particularly in 1969, the Mustang Boss 429, Camaro ZL1, and the Charger Daytona Hemi were the most powerful muscle cars you could buy from each ofthe "Big Three" in the US.However, while most of these models were built in a handful of quantities, there were some much rarer than usual. Even rarer when manufacturers ditched the naturally aspirated engines and equipped them with forced induction, like a massive supercharger.In order to find the rarest American muscle car with a factory equipped supercharger, we had to dig deep and, naturally, it led us to the 60s. This extremely rare '60s muscle car is also based on a highly collectible version of a rare high-performance 2-door coupe. Of course, it has Carroll Shelby's magic touch. The Shelby GT350 Paxton Is The Rarest Supercharged Muscle Car 1966 Shelby GT350 Paxton Supercharged V8 engine Events Timeline Joe Granatelli of Studebaker Corporation’s Paxton Products Division approached Carroll Shelby with the idea of a factory supercharged kit for the GT350 in 1965. A pre-production prototype GT350, the SFM5010 was used to install the first “Cobra” Paxton supercharger kit. Granatelli impressed Shelby, and convinced him to offer a supercharger option with the GT350 in 1966. The 1966 Shelby GT350 Paxton is the rarest muscle car with a factory supercharger, with only 11 examples ever made. Two prototypes were manufactured in 1965 and one of them was retailed to a customer, classified as "demo" on the original invoice. However, officially, production of the Paxton supercharged Shelby GT350 only started in 1966, and was discontinued after a single model year.The idea of a supercharged Shelby GT350 was conceived by Joe Granatelli, who was working with the Studebaker Corporation’s Paxton Products Division. In 1965, Granatelli approached Carroll Shelby with his idea of a GT350 with a factory-equipped supercharger kit. Carroll Shelby loaned Granatelli a pre-production prototype GT350 with the SFM5010 code name.Seeing the result of the development of the supercharged V8 engine, Carroll Shelby was impressed. As a result, he agreed to make a special batch of special-order supercharged Mustang GT350 only for the 1966 model year. Additionally, Shelby ordered additional supercharger systems as options for the brand's catalogs as well.Though the supercharged GT350 wasn’t produced in large numbers, its legacy lived on as forced induction became more common in muscle cars. By the late 20th and early 21st century, cars like the Ford Mustang SVT Cobra, Dodge Hellcat, and Chevrolet Camaro ZL1 used factory superchargers to enhance performance.The 1966 Shelby GT350 Supercharged can be seen as a precursor to these modern high-performance supercharged vehicles. Only 11 Units Of The GT350 Paxton Were Built, 9 Survive Today Via: Mecum AuctionsAccording to Mecum Auctions, Shelby and Paxton developed two prototypes of the Shelby GT350 with a factory equipped supercharger in 1965. The original supercharged GT350 prototype with the code name: 5S425 last went under the hammer in 2020.In 1966, when Shelby put the GT350 Paxton into production, only 11 examples were made, making it the rarest muscle car with a factory supercharger. Mecum Auctions states that only nine examples of the 1966 Shelby GT350 Paxton with the 390 hp supercharged V8 engine survive today. In contrast, Shelby built a total of 2,367 units of the standard GT350 model. All 2,378 units in total were the 2-door hard top coupe models, as Shelby only introduced the GT350 convertible in 1968. Rare Supercharged 1966 GT350 Paxton Is Worth Twice The Money 1966 Shelby GT350 Paxton Wheel 1966 Shelby GT350 Paxton Current Values (Source: Hagerty)Shelby built just 2 prototypes of the Paxton supercharged GT350 in 1965. 11 production models were manufactured with 390 hp in 1966, and only nine examples remain. This rarity makes the '66 Shelby GT350 Paxton twice as valuable as the standard GT350. While the standard GT350 in Concours condition is worth $306,000, the GT350 Paxton is valued at $650,000 according to Hagerty. In excellent condition, a rare GT350 Paxton is worth $575,000, while a good example sells for an average of $488,000. Even a fair condition model is worth $349,000. Paxton Supercharger Heavily Improved The GT350's Performance 1966 Shelby GT350 Paxton Supercharged V8 engineThe standard 1966 Shelby GT350 was equipped with the 289 cu-in naturally aspirated V8. This engine developed 306 hp and 329 lb-ft of torque with a Holley four-barrel carburetor as standard. The Shelby GT350 claimed 0-60 MPH in 6.6 seconds.In the 1966 Shelby GT350 Paxton, the 289 V8 retained the four-barrel carb, while pairing it with a Paxton supercharger. This elevated the performance of the engine significantly. The Paxton centrifugal supercharger significantly increased airflow into the engine, allowing it to make 390 hp and 420 lb-ft.The supercharger resulted in an 84-horsepower and 91-pound-feet increase in power and torque. The '66 Shelby GT350 Paxton claimed an estimated 140-mph top speed, which was mighty impressive for its time.The engine was mated exclusively to a 4-speed Borg-Warner T-10 manual transmission as standard in the GT350. The same transmission was carried over to the Paxton Supercharged model, as it was known to be durable, smooth enough, and the close ratios allowed for improved acceleration. The standard Shelby GT350 was available with an optional C4 3-speed automatic, but few were built as enthusiasts preferred the manual gearbox.For these reasons, collectors of classic and muscle cars consider the 1966 Shelby GT350 Paxton as the crown jewel of the Shelby line up.