The Hertz Penske GT is a customized Mustang only available through 180 rental car locations.

If your idea of a rental car is something stripped-down and so slow it can barely get out of its own way you may be in for a surprise next time you visit a Hertz rental counter.

The number one daily rent-a-car company is teaming up with Penske Racing to create a limited-edition Ford Mustang that will join the new Adrenaline Collection of performance cars.  Intended to let customers “Relive the 60’s and 70’s muscle era,” according to the Hertz website, the Adrenaline Collection already includes the Chevrolet Camaro SS and the Dodge Challenge R/T.

The Hertz Penske GT, as it’s been dubbed, is clearly not your typical rental car.  It starts out life as a 420-horsepower Shelby GT but then gets a major makeover by the Penske team, which bolts on a modified air intake and freer-breathing exhaust.  The engine computer gets a new chip that allows increased performance.  The transmission gets a more aggressive set of gears. And the final touch is a set of Brembo brakes.

The partners aren’t releasing final horsepower numbers, but a few industry watchers polled by TheDetroitBureau.com suggest that all those modifications should readily push the Hertz Penske GT over the 500-hp mark, if not higher.

Distinguished by its black paint job and contrasting gold race stripe, the modified Mustang will not be available for sale, Hertz cautions.  If you want to get behind the wheel you’ll have to visit one of 15 airport locations that offer the Adrenaline Collection.

And don’t look for any online discounts.  The Hertz Penske GT will set you back $180 a day, or $800 a week.  And that’s for a maximum of just 100 miles a day.  You better expect to fill up the gas tank before returning the car as all those modifications will suck down fuel in a hurry.

Hertz has been steadily expanding its range of higher-end products, with an increasing emphasis on performance cars and exotics, including Porsches and Ferraris.  But having long been owned by Ford, the rental company has offered special Mustangs on a number of occasions, including the GT350H tweaked by Carroll Shelby back in 1966.  And even it was sold by Ford, Hertz offered the special Mustang GT-H in 2006 and 2007.

The link to Penske Racing isn’t as odd as it might seem.  Hertz is currently sponsoring one of Penske’s NASCAR entries, the #22 car driven by Joey Logano.

There’s a growing market for exotic rental cars, once the purview of just a few specialty firms in places like Beverly Hills, where visiting celebrities wouldn’t be seen in something as pedestrian as a Taurus or Corolla.

Hertz rival Enterprise has its own Exotic Collection and, according to USA Today, rental days for the various performance models have increased 50% over just the last year.