SOMETHING OLD, SOMETHING NEW; Ford and Shelby celebrate an almost 50-year union with a new baby.(News)

Byline: NATALIE NEFF

Marriage is rarely an uncomplicated affair. Dalliances with outside parties have felled even the mightiest of unions, but the bond between Ford Motor Co. and Carroll Shelby has endured despite its share of acrimony and a two-decades-long case of wandering eye.

In fact, the union has flourished over the past few years, so much so that the happy (and busy!) couple have spawned a whole clutch of cars recently, including the Ford Shelby Cobra concept seen at the 2004 Detroit show, the GR-1 concept from last year's show and an available-for-rent-soon-at-a-Hertz-near-you GT-H. They are now set to welcome the latest addition to their family, the production Shelby Mustang GT500.

Based on the redesigned-for-2005 Ford Mustang and first seen in concept form at the New York auto show, the GT500 turns the Mustang-ness of the entire package-from styling to performance-up a notch. The car's handsome, retro-inspired looks are bulked up with the addition of lowered side sills, a deeper front fascia with chin spoiler, larger grille, rear diffuser, domed hood with functional air scoops, rear decklid spoiler, contrasting go-fast "Le Mans'' top stripes and huge snake emblems everywhere you look, all together giving it the appearance of a serious road machine.

Of course the original Shelby GT500, which debuted in 1967, was a serious road machine, cranking out 355 (gross) hp from its 428-cid big-block V8. The power, the styling, the renegade attitude even seduced the likes of Hollywood, with a GT500 named Eleanor serving as the star of the original Gone in 60 Seconds movie.

In place of the Mustang GT's 4.6-liter 300-hp V8, the new GT500 employs a 5.4-liter V8 feeding off a supercharger forcing 9.0 psi of air through a specially designed intake manifold and aluminum heads. Its SAE-certified 500 hp makes the Shelby not only appropriately named, but also the most powerful Mustang ever to roll out of Dearborn (or Flat Rock, Michigan), says Ford.

Shuttling all that power to the ground is a Tremec six-speed manual transmission, a familiar unit to those who have driven past Cobras and Dodge Vipers. It's a fairly easy to use box, with a clutch pedal now tuned to match. Gone is the quadriceps-building clutch of the last Cobra, thankfully.