For 2010, Ford sells a Mustang Shelby GT500 with a base price of $46,725, but the company also sells a very nice, fun-to-drive Mustang with a base price of $21,395. Even at that price, the base Mustang is well-equipped, and with a styling update for 2010, looks great.

So why, then, would someone spend twice that much on the top-of-the-line Mustang? That's always been the challenge for Mustang designers and engineers — pack enough content, attitude and moxie into the premium versions to justify the price.

And man, they've nailed it with the 2010 Mustang Shelby GT, starting with the 5.4-liter supercharged V-8 engine that's rated at 540 horsepower. In the past, some of the most powerful Mustangs simply didn't feel as strong as their horsepower ratings suggested. This one does, and then some.

And while Ford has improved fuel mileage over 2009, the EPA rates it at 14 mpg city, 22 mpg highway, on premium gas, of course. This earns it a $1,000 federal "gas guzzler" tax. The only transmission offered is a good-but-not-great Tremec six-speed manual. No automatic is available.

Inside, the interior will be familiar to any Mustang owner, but it is decidedly more upscale, with excellent front bucket seats. Rear seats exist, but are better for groceries than humans. The test car had the $2,195 "electronics package," consisting mostly of a very user-friendly navigation system. The only other option was high-intensity headlights at $525. With shipping and the guzzler tax, list price was $51,295.

On the road, the GT500 is a rocket ship, with superb, linear acceleration — Ford claims a 0-to-60 mph time of 4.3 seconds — and brakes that are more than up to the task of hauling down a car that weighs nearly 4,000 pounds. Despite the weight, the GT500 feels very light on its feet on winding roads. And despite the stiff suspension, the ride is far more comfortable than you'd expect on all but the roughest pavement.

White with red stripes, the test car drew plenty of attention, especially from police officers who appeared to squeeze the trigger on their radar guns just a little harder when we drove by.

Finally, know this: Ford has just announced that the 2011 model will have 10 more horsepower, from a new aluminum engine that weighs 102 pounds less. More power was not on my list of things the 2010 GT500 needs, but I'll cheerfully test it when it shows up.

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2010 FORD MUSTANG SHELBY GT500:

—Base price: $46,725

—Price as tested: $51,295

—EPA rating: 14 miles per gallon city driving, 22 mpg highway

—Details: Front-engine, rear-wheel-drive performance coupe with a supercharged 5.4-liter, 540-horsepower V-8 and a six-speed manual transmission.