’65 Shelby GT350: How the Mustang Got Fast

The Ford Mustang’s first performance variant, the Shelby GT350, took “a secretary’s car” and transformed it into a racecar.

Shelby “Saves” the Mustang

The Ford Mustang has a long legacy (sixty years this April!), and for most of that time, it’s been a fast car, both on the street and on the track. But the Mustang did not start out as a performance car. Originally, the Mustang was a Ford Falcon in a tuxedo, as sleek and muscular as its namesake but not especially powerful. The default Thriftpower straight-sixes were laughably weak at 120 horsepower and even the HiPo 289 V8 topped out at 270 horsepower. Indeed, the first year ‘64 ½ Mustang was derisively referred to as “a secretary’s car” for its mundane driving experience.

So, how did the Mustang transform from a fast-looking car into a genuinely fast car? For that we can thank our patron saint of speed, Carroll Shelby.

Making the Mustang a Racecar

65 Shelby GT350 Engine - shelby.com
65 Shelby GT350 Engine - shelby.com

In late 1964, Ford’s Lee Iacocca worried his wildly popular new Mustang might peter out for lack of a performance variant. Iacocca felt a racing-capable Mustang was sure to keep the youth market’s attention. The only problem, the SCCA (Sports Car Club of America) had rejected the car because it was a 2 + 2 rather than the two-seater homologation rules required.

But Iacocca knew someone who might be able to help, Carroll Shelby. Shelby was already hard at work perfecting Ford’s GT40 to race at the 24 Hours of Le Mans. According to Shelby American designer Pete Brock, Iacocca rang him up and asked how Shelby might get the Mustang qualified. Shelby quipped that Iacocca “wanted him to make a racehorse out of a mule.” To do so, Shelby called his friend John Bishop, president of the SCCA, and got Bishop to approve the Mustang so long as it was modified into a two-seater. And thus, Shelby entered his second major project with Ford, making the Mustang race-worthy.

The Shelby GT350 Takes Shape

65 Shelby GT350 Tachometer - shelby.com
65 Shelby GT350 Tachometer - shelby.com

SCCA rules gave the option of modifying either the engine of a car or the chassis and running gear. Shelby decided to go with the latter, making use of Ford’s 289 Winsor V8 as the Mustang’s powerplant, and then modifying the Mustang’s chassis instead.

The 289 was already the Mustang’s high-performance option and Shelby added a four-barrel Holley carb, a “high-riser” intake manifold, dual side exhaust, and Tri-Y headers. The result was an output of 306 horsepower and 329 lb.-ft. of torque sent to a Borg Warner four-speed manual.

The more thoroughgoing were the modifications to the chassis and running gear. Shelby added front disc brakes and bigger drums in back, Koni shocks in the rear, and revised the front suspension as well. A Detroit locker rear differential was also added, and the battery was moved to the trunk for easier access and better weight balance (’65 only before it was returned to the engine bay). A tachometer and oil pressure gauge supplemented existing instrumentation. To meet the two-seater requirement Shelby simply removed the rear seats and replaced them with a shelf that stored the spare tire.

65 Shelby GT350 Front - shelby.com
65 Shelby GT350 Front - shelby.com

The racing version, the GT350R, came with additional alternations that stripped components for weight, like swapping plastic windows for glass. Racing staples like a larger gas tank, rollbar, and wider wheels were added. Additional fiberglass replaced steel in the front of the car, a larger radiator was added as was an oil cooler for the rear differential.

Shelby American’s designer Pete Brock was tasked with the car’s look. He added a lightweight fiberglass hood. Though he’d planned for a rear facing hood scoop, to pirate low pressure directly in front of the windshield to force-feed air, the scoop ended up facing forward to meet buyers’ aesthetic expectations. Brock did get his wish on the car’s paint job, Wimbledon White with blue rocker panels. Brock’s personal touch was the addition of a pair of optional (dealer applied) Le Mans-style racing stripes down the middle, inspired by the ’51 Le Mans car driven by Briggs Cunningham. With the high-performance upgrades in place and the look cemented, one question remained: what to name the new car? The 350 in GT350 was simply the distance between the production and racing shops at Shelby American.

’66-’70 Shelby GT350

65 Shelby GT350 Interior - shelby.com
65 Shelby GT350 Interior - shelby.com

The Shelby GT350 proved a potent force in Trans Am racing and for Shelby American in particular. Test driver and engineer Ken Miles drove the GT350 to a win in its first race, in February of ’65 at Green Valley Raceway in Texas.

Year-over-year changes for the Shelby GT350 included the addition of a three-speed automatic and fold down rear seats for 1966. That year rental car company Hertz ordered 1,000 GT350s in black and gold livery, as part of a “rent a racecar” promotion. As part of the deal, the cars were returned to Ford following their rental life, refurbished, and stamped as GT350H cars (though many reportedly returned minus some of their performance parts). By this time, Shelby American had hit tough financial straits and Shelby bowed out of constructing the GT350 and GT500, though he continued to provide direction and input.

1967 Shelby GT 500 - fordheritagevault.com
1967 Shelby GT 500 - fordheritagevault.com

In 1967, came the addition of the Shelby GT500 (thus named for 500 being bigger than 350). It ran Ford’s 428 V8 equipped with two Holley four-barrels good for 355 horsepower. The Mustang’s redesign that year carried over to the GT350 which received additional embellishments from Shelby that included a more aggressive front end, new sequential taillights, and a rear spoiler. In 1968, the GT350 received a new 302 V8 (250 horsepower) that could be optioned with a Paxton supercharger adding another 33 horsepower.

The Mustang received another visual overhaul in 1969, but this time most of the GT350 tweaks were Ford’s work as Shelby’s partnership with the company was coming to a close. This final iteration saw the introduction of the 351 Winsor V8 to the GT350, good for 290 horsepower. Production on those first-generation Shelby Mustangs concluded in 1969, with some late production cars receiving minor cosmetic tweaks and a 1970 model year designation.

65 Shelby GT350 Exterior - shelby.com
65 Shelby GT350 Exterior - shelby.com

Though the original GT350 didn’t last long, the association of Shelby and the Mustang would return in 2005 and be applied to numerous Mustang variants through 2022.

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Chris Kaiser

With two decades of writing experience and five years of creating advertising materials for car dealerships across the U.S., Chris Kaiser explores and documents the car world’s latest innovations, unique subcultures, and era-defining classics. Armed with a Master's Degree in English from the University of South Dakota, Chris left an academic career to return to writing full-time. He is passionate about covering all aspects of the continuing evolution of personal transportation, but he specializes in automotive history, industry news, and car buying advice.

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