With 774 ponies at 7,000 rpm and 648 lb-ft (878 Nm) at 4,400 rpm, the SRT Hellcat-ified Challenger will have to put its money where its mouth is in a quarter mile drag race against the HPE750. That’s if the rear rubber can stand the punishing off-the-line acceleration. Still, with a 0 to 60 mph (96 km/h) coming in just 3.4 seconds and an official 1/4-mile run of 10.9 seconds at 133 mph, the SRT Hellcat and Hennessey’s machine are pretty close.Take into consideration that the Hennessey HPE750 is $69,374, while the hell-bent for leather Challenger is a smudge over $60,000. Does the $10k difference matter? Not at all, especially when you consider that a thorough muscle car can shame Italian exotica for less than a 2015 Porsche Cayman GTS. Famous car aficionado Jay Leno took his filming crew to find out what’s what with the HPE750 Mustang for that matter.But the 207.9 mph (334.5 km/h) top speed this baby is able to hit on a long enough track speaks volumes. It’s the fastestto date and Racelogic VBox 3i GPS data logging systems prove its potential. So what did John Hennessey’s team give this pony to make it so damn fast?Starting from a 2.9-liter Whipple blower, the HPE crew added upgraded everything to make the 5.0 V8 more durable and powerful. And some carbon fiber bits and bobs for more visual drama, as expected.Only 500 examples will be manufactured by Hennessey for the 2015 model year and all of them come with a 3-year/36,000-mile limited warranty. “If at first you don’t succeed, just add more horsepower and rpm and try again,” said HPE numero uno John Hennessey. “It’s pretty cool to be able to offer an American muscle car that delivers supercar performance for under $70,000.