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Fast Lane Flashback

The 1965 - 1970 Shelby GT350 & GT500 Mustangs

By: Lawren Dame \ Associate Editor \ July 14, 2014

Archived Articles

The Shelby Mustang—a name so familiar and renowned that it rolls off the tongue almost as easily as it rolls down the road, certainly one of the most enduring visions of muscle and power ever built.


It wasn’t always this way, however. In the mid-1960s the Mustang was not quite up to par with its possibilities. By the summer of 1964 it was decently successful, with its first high-performance engine, a 271 horsepower 289 cubic inch V-8; however, Ford had the vision to transform the Mustang into a vehicle with strength and prowess—a true muscle car. It was then that Ford Motor Company enlisted the aid of the racecar genius, Carroll Shelby, to lead such a task. 



Shelby’s skilled track testing determined that the Mustang lacked quicker steering, better brakes, and—most importantly of all—horsepower. The result: the 1965 Ford Mustang Shelby GT350. This vehicle was as the closest thing to a street-legal racecar, with modified high-performance suspension, a lighter fiberglass hood with air scoops, fast-ratio steering, larger disc brakes, and engine improvements that boosted the horsepower from the factory’s 271 to 306 horsepower.


The backseat was removed and replaced with room for a spare tire and fiberglass cover, which allowed the GT350 to be qualified as a sports car rather than a racecar—though the inside boasted racing seat belts and full instrumentation. The car was fitted with Koni adjustable shocks as well as larger sway bars in the front and back, 15 inch silver wheels, and a Detroit Locking rear complete with traction bar brackets. Only one transmission was available; the Borg Warner T-10 4-speed manual.


As for the Mustang’s appearance, it received side-exit exhaust pipes, a brand new paint job with a white body and blue stripes racing up and down its hood and sides, and Glasspack mufflers to aid sound enhancement. Though its horsepower was high, the Mustang was smaller and lighter than most of the muscle cars that occupied Detroit’s streets, and therefore was elevated to a level of its own. Unlike any other muscle car before it, the Shelby Mustang GT350 was one that could without a doubt handle well. 



By 1966, the GT350 had lost its Mustang label and was instead simply known as the Shelby GT350, though in appearance it was nearly identical to the previous year’s model. The paint job, previously exclusively white, now included blue, red, green, or black, all with white stripes. The engine blocks experienced a color change as well; Mustang engine blocks were now painted a dark blue as opposed to the previous year’s black. Factory extractor vents were replaced by Plexiglas rear quarter-panel windows. A SelectShift 3-speed automatic was now available, as well as a Paxon supercharger, which boosted horsepower to numbers in excess of 400. Over-rider traction bars were no longer used, and the battery was no longer relocated to the trunk.


During this year, Shelby and the Hertz Corporation made a deal to produce a special line of rental car GT350s that would be refurbished and sold to the populace after serving as rentals. Hertz was given exclusive ownership of 1,000 such cars. These cars would be dubbed as GT350-H models, and the first models were white with blue stripes, much like the original 1965 GT350s. The remaining majority came with black paint and gold Le Mans stripes, with a black interior. These Hertz models wore chrome Magnum 500 wheels, and most received auto transmission. Of the Hertz cars, the first 85 were produced with a four-speed manual transmission and advertised as “Rent-a-Racer” cars, and were even sometimes used at Sports Car Club of America (SCCA) events as production class cars.


Additionally, there were a total of 1,373 fastbacks produced in 1966, including 252 early production model GT350s which originated as 1965 Mustang K-Code Fastbacks



The refreshed 1967 Ford Mustang was a larger and heavier breed to work with offering a 289-cubic-inch V-8 and an optional 390-cubic-inch V8 from the factory. Shelby shoehorned in a 428-cubic-inch V8 which generated 400 horsepower, although it was still marketed as 355 hp to pacify insurance companies. This new creation of American muscle was named the GT500.


As for the GT350, it kept its 289-cubic-inch V8 engine, but was forced to lose its original power-enhancing steel-tube exhaust headers due to newer noise regulations. Though the horsepower for the GT350 remained advertised at 306, in reality, it pushed 290 hp.

In terms of appearance, the Shelby Mustang underwent quite a few upgrades, from a custom fiberglass front fascia and two additional headlights in the grille’s center, to a multitude of functional scoops, covering the hood, sides of the lower body, and behind the windows. The interior of the Mustang was either black or parchment, outlined with either a two-point or four-point roll bar. The chassis could now handle more sharply, and racing-style modifications were installed in the interior, including a new steering wheel, extra gauges, and built-in inertia-reel shoulder harnesses. The trunk lid of this Mustang received a functional air spoiler, flanked by wide taillight clusters barrowed from the 1967 Mercury Cougar, minus the chrome trim.  Each 1967 Shelby GT350 and GT500 came with rocker panel stripes and emblems on the front grille, fender, and rear deck. Each contained a pop-open gas cap with a Shelby Cobra cover as well. The car was updated with completely new power steering and brakes for this year, as previous models were similar to racecars and therefore had no need for power accessories.

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This GT500’s only setback may have been its heavier build—though a fast car, its 0-65 mph time of 6.5 seconds was not fast enough for everyone. What it may have lacked in speed it certainly made up for in style, with its longer hood and full-fastback styling.  Whereas previous Shelby models emphasized performance over luxury, the GT500 emphasized a fair balance of both worlds. It was this factor that made the 1967 Mustang such a success, with 3,225 sold total that year.


Though the Shelby Mustangs were indeed a success, unrest was brewing between Carroll Shelby and Ford. In September 1967, production was moved to the A.O. Smith Company in Ionia, Michigan, under Ford control.  Shelby American had substantially less involvement after this time. This marked the beginning of turmoil in their partnership, however, would continue throughout the next few years.



For the 1968 production year, both models received the Cobra nameplate, and now went by Shelby Cobra GT350 and Shelby Cobra GT500; each was available in convertible form as well. In February the Cobra GT500-KR was released, “KR” standing for “King of the Road”. The KR was armed with a 428 cubic-inch Cobra Jet V8 with a rating of 335 horsepower—but in reality, with its torque rating of 440 foot-pounds at 3400 RPM, was actually closer to 400 hp. The “Cobra” update to the name of these vehicles reflected Ford’s new use of the name in all of its performance parts and vehicles like the Cougar, Cyclone and Fairlane models.


The Shelby Cobra Mustangs received an updated fiberglass nose in an attempt to give it a more aggressive appearance, and the hood was now embellished with two front hood scoops and a pair of rear hood louvers.  A 302 cubic-inch V8 took the place of the GT350’s 289 cubic-inch V8, and used an aluminum ‘Cobra’ intake manifold and Holley 600 cfm carburetor.  This new engine was rated at 250 horsepower. The GT500’s engine was a 428 cubic-inch Police Interceptor V8, and this year it came with just a single 715 cfm carburetor mounted on an aluminum manifold. Very few GT500s still carried the 428 low riser intakes, however available with an automatic transmission only.

Once the KR was released, it took the place of the GT500 entirely. Cobra Jet emblems graced the dashboard, fenders, and gas cap lid of these muscle cars. All KR Cobra Jet engines had traction-lock 3.50 rear end and functional Ram Air Induction. Ford boasted that this 428 Cobra Jet option price was affordable for all, as it was cheaper in comparison to the other high performance engines available at the time. This engine saw much success at races, winning Super Stock Eliminator Champ at the 1968 Winternationals. 



In the penultimate year of production for the Shelby Mustangs, their Cobra title was dropped and was once again sold as the Shelby GT350 and GT500. Their appearances changed dramatically—among other style and design decisions, which unfortunately lacked much involvement on Shelby’s part. The redesigned 1969 Shelbys received a 4-inch increase in body length, taillights from a 1965 Thunderbird, fiberglass front fenders and hood, and 7-inch headlights at the head, as well as the standard stripes and Cobra emblems. The Shelby’s interior was available in black or white, and both the GT350 and GT500 remained available in fastback as well as convertible format.

As for engines, the GT350 went with the 290 horsepower version of the 351 Windsor, with the addition of an aluminum intake manifold. The GT500 went with the 428 CJ.

In the summer of 1969, Carroll Shelby moved to terminate his agreement with Ford. Shelby’s distance with Ford had grown significantly wider since the days of racing the GT40 at Le Mans and victory against Ferrari. This distance as well as the disagreements which had been brewing over the past few years finally culminated in this unhappy ending. 



Though Shelby and Ford were no longer in partnership, there were still Mustangs to be sold. About 789 of these muscle cars had gone unsold in 1969. Therefore, instead of producing more, the unsold 1969 Shelbys were issued new 1970 Vehicle Identification Numbers under the supervision of the FBI, and gained two matching black stripes on the hood as well as a Boss 302 type chin spoiler.


Though Shelby Mustangs were no longer in production, a few 1971 and 1972 models were produced per the request of Claude Dubois, a Belgian Shelby dealer. Shelby built 14 1971/1972 Mustang-based models for him, marketing them as the “Shelby Europa” and selling them exclusively in Europe.


In the mid-70s, Ford would go on to infuriate Shelby by using the Cobra name on the Pinto-based Mustang II. In 1988 Shelby would subsequently sue Ford for using the GT350 name on a Mustang which wasn’t his. 

However, by the late 90s nearly 40 years later, the two were able to set aside their differences, and Shelby aided Ford once again in developing the new 2005 Ford GT to celebrate Ford Motor Company’s 100th anniversary. Ford and Shelby would remain in good standing for the remainder of Shelby’s life, and every Mustang produced henceforth bears a hint of this great man’s legacy.


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