That was certainly the case with one of ex-racer Carroll Shelby's most famous cars. For 1965, he began production of hopped-up Mustangs at his shop in California. For those first couple years, his 'Stangs, called GT-350s, were barely-disguised competition tools.

With a road-racing suspension setup, high-strung small-block V8, and lack of a backseat on which to haul buddies, those original GT-350s weren't a popular pick with the burger-joint crowd. And that was fine with Ford, at least at first -- Shelby's cooperation on the Mustang was initially sought to give competition credibility to Ford's pioneering ponycar, which GT-350s did handily by winning sports-car races.

But starting with the '67 model year, Ford began expecting Shelby's machines to speak to a more mainstream performance crowd -- the typical muscle-car buyer.

Signaling this shift toward street appeal over race-track prowess were mandatory power steering and power brakes, along with a number of optional comfort and convenience features, including air conditioning, tilt steering wheel, and tinted glass.

And, perhaps most importantly, a backseat was now standard.

But despite the added weight of such amenities, Shelby's machines hadn't lost their bite. Although the base GT-350's V8 was now somewhat tamer, that model for '67 was joined by the new GT- 500, powered by a torquey 428-cid big-block V8 rated at 360 hp.

For '68, the GT-500 packed an even bigger wallop, with the midyear introduction of the GT-500KR "King of the Road," which had a 428 that was some 40 hp stouter yet. Also that year, the Shelby Mustang's fastback bodystyle was joined by a convertible, to further appeal to the boulevard cruising set.

Development and production of Shelbys continued along similar lines into the next generation of Mustangs, ending in 1970.

Today, muscle-car fans are divided on which of the Shelby Mustangs are the greatest -- the almost race-ready early versions, or the punchier, plusher, more street-appropriate later ones. Regardless, any flavor of Shelby Mustang is counted among the great performance cars, a fact clearly reflected in the hefty prices these cars command nowadays.

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About the Author

David Bellm is a seasoned test driver and automotive historian. His work has been featured in a wide variety of online and print publications.

A Quick Note From The Publisher... If you like the article above, you may be interested in the following article which is also related to Mustangs... Boss Mustang: Then and Now The Mustang has been loved by car enthusiasts since it was first introduced back in the Swinging Sixties. In fact, the Mustang had one of the most successful auto launches in history! People were enthralled with a car that had sleek sports car looks and a smooth, powerful engine. The Mustang was the best of both worlds... the ultimate status symbol and the most powerful car of its time. Boss Mustangs were infused with a powerful engine, a sturdy design and stylish good looks. Each series in the Boss line was slightly different in design and engine, but all were excellent performers. The first of the Boss series, the 302, came out in 1969. It had a 302 (surprise!) engine that was documented 290 hp. Owners of this vehicle would later dispute this by saying the horsepower was closer to 350. This vehicle came standard with exterior stripes and front spoilers. The rest was optional and could be added for extra fees. The Boss 429 was available in 1969 and 1970...

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