Option Code S: The 1966-'67 Paxton Supercharged Shelby GT350

Debuting as a 1964 model, the Ford Mustang became an instant sales hit and ushered-in the “pony” car segment where it still holds title today. But before the ink was dry on many ‘64 Stang registrations – or Carroll Shelby’s new contract with FoMoCo for that matter – the Le Mans winner and Cobra-creator was preparing a special version that would become a legend.

Badged in 1965 as the GT350, this hopped-up and stripped down, hardcore race-ready pony, could roll on the street or SCCA sanctioned track and put the beat-down to any and all competition. As good as it was however, Shelby was always looking for more power and greater performance.

That’s where the Granatelli’s (Joe, Vince and Andy), come-in. The trifecta of racing brethren where a wealth of automotive experience, with Joe being a mechanic/engineer at Indy and Andy being CEO of STP, yes, that’s STP race lubricants and later founders of Granatelli Motorsports. At this time as well, the Granatelli’s owned Paxton Automotive, a company started by Robert Paxton McCulloh which was the leading producer of centrifugal superchargers-originally for flathead Fords, Studebakers, and Packards. As the new Mustang was galloping from dealer’s lots, the Granatelli’s wisely felt that V8 models would benefit from a Paxton supercharger and with Carroll Shelby saddling-up an even hotter version, a new market had opened.

Word has it that in early 1965 Andy Granatelli approached Shelby with the idea of fitting a Paxton blower into a GT350 (which he may have already done to his own), to increase its performance. Slightly insulted and yet intrigued with the idea, Shelby loaned him a GT350 for the install.

By the summer of ‘65 Andy or brother Joe, returned to Shelby American’s HQ at LAX airport with a proper-supercharged GT350 Mustang ready for demonstration. According to legend, Shelby jumped into a naturally breathing, 2200-lb 289-cid V8 Cobra-and it was on- as the tale goes, the snake got kicked by the pony, Shelby was thrilled and he ordered-up a bunch of Paxton blowers.

Shelby wasted little time in building a couple prototypes, originally to be named the GT350 S for obvious force-induced reasons, but then, as he often did, he changed his mind and decided against it. Instead, the Paxton blower package could be special ordered and factory installed on a GT350 upon a customer’s request and for an extra $670.

Shelby massaged the 289-cube V8 to pull in 306 horses, but the fruits of the Paxton blowers on the GT350s equated to a jump to around 390 horsepower, with some sources saying as much as 450-hp when properly tuned. With zero to 60 launches in the mid 5s and a top speed of 150-mph, the Paxton GT350s were without a doubt the super cars of their day, and not to shabby even by today’s standards.

Between 1966 and ’67, Shelby American built approx 46 Paxton supercharged GT350s, (11 in ’66, 35 in ’67) all featuring the Paxton blower and necessary modifications, Autolite 4-barrel carb, a Carter high volume fuel pump and a pair of specific chrome-bezeled, under-dash-mounted gauges to monitor the manifold pressure and vacuum operation. And this was on top of any and all regular Shelby GT350 features and options. The Paxton supercharger package was also made available as an over the parts department counter kit and could be installed on any GT350 or standard 289-cid V8 Mustang.

Beyond the handful of documented Shelby-built Paxton supercharged GT350s, knowing the total number of V8 Mustangs equipped with the package – which was available until 1970 – may be as elusive a fact as locating the final resting place of the lost Ark of the Covenant.

With that said, the Shelby GT350 Mustang was a legendary car, created by a legendary man, and the Paxton supercharged versions carry that legend to an even higher level. Carroll and the Granatelli’s, may they rest in peace, are probably looking down at these Hellcats and Demons and saying, that’s great, but we did that back in 1965.