This is the new 2015 Dodge Challenger SRT Hellcat, complete with that all-new pyrotechnic 707bhp supercharged V8. This is not just the most powerful Challenger ever made, it’s also now the most powerful muscle car you can buy – sweeping aside the 662bhp Shelby GT500 – and offers the most horsepower per dollar ($85 per nag) of any car on sale in the US. Just to contextualize it, in the rank order of most powerful production cars on sale in the world, this Hellcat sits just above the Lamborghini Aventador and just below the Ferrari F12.Plenty. The tightened up exterior design so it now reflects the original 1971 car more faithfully. New interiors also borrow heavily from the Seventies car’s features. There’s an eight-speed automatic – in place of the old six-speeder – better instruments and electronics across the range, including all the latest anti-crash stuff, revised three-mode electric power steering and a host of other nice details like an active exhaust.Kind of, but it’s a very thorough one. Challenger sales have been up every year for the last five years, so it wouldn’t make sense to change it dramatically. But there have been some substantial changes, particularly towards the top end of the model line up. There are now eight trim levels that range from the humble SXT on the 305bhp V6-engined cars all the way to the hellacious Hellcat.It’s not badged as anything more than the SRT model now – the engine name isn’t on the car anywhere, which seems like a trick missed. The only visual tells are the air intake where the left drivers lamp should be, the supercharged badge on the wing, and its ability to disappear in a cloud of fire and brimstone in an instant. Also note that there are now two SRT models in the range – beneath the Hellcat is the SRT 392 HEMI Scat Pack Shaker.The Scat Pack (stop sniggering at the back) is a collection of go faster goodies that lift the performance by up to 113bhp and 65lb-ft, add an active exhaust, upgraded suspension and better brakes among a long list of detailed upgrades. So you want it if you can get it. The Shaker bit refers to the air cleaner poking out of the bonnet. It allows the engine to breathe more deeply, and make more power, so you want that, too. They are quite a bit cheaper than the Hellcat-equipped cars, and not a whole lot slower.Not really. The Challenger is a proper four seater and the Viper is a cramped two-seater coupe that will still demolish the Hellcat, even in a straight line. Completely different products for different purposes.You’re right. Company insiders hinted that the Viper is being completely rethought. Now that Fiat and Chrysler are one company, all technology is being shared across the company – including Ferrari’s for the first time – which opens the door to a possible hybrid Viper. That car could use the Hellcat engine and add an electric motor giving the Dodge supercar over 900bhp. The company is also researching possible four-wheel drive systems for the car, which wouldn’t appear for a couple of years yet…It drives much better than you’d think a car weighing over 2,000kg could and should. Unlike the nervy Shelby GT500, it doesn’t ever feel like it’s going to flick you off the road or track if you don’t concentrate 100 per cent. Its attitude is fully – and hilariously – adjustable on the gas almost as much as with the wheel. But it never feels anything other than neutral and on your side, which allows you to enjoy all the performance on offer. It also stays remarkably composed when braking or cornering heavily, so you can indulge your right foot without getting into too much bother. It might look like the ’71 car, but it handles like a modern muscle car should.It’s much the same. With a simple launch control set up, you can smoke the tyres at will and rattle off sub 12-second quarter miles (sub 11-seconds on drag radials) with as much effort as treading on an insect. There’s plenty of suitable smoke and drama outside the car. And plenty of timers and graphics inside the car to let you know how you’re cooking.On the road, the lack of chassis mushiness remains alongside a new, more plush and hushed cabin. It’s comfortable and fun to drive at regular road speeds, the (hydraulic on the Hellcat only) steering and eight-speed auto box – the first time the hi-torque version of the TorqueFlite box has been used – being the standout features here. The six-speed manual (borrowed from the Viper) is also on offer for traditionalists. It’s big, comfortable, raw enough to be fun, refined enough to live with, makes a great noise and looks the part.There will come a day in the not too distant future when we can’t drive V8s anymore. Particularly V8s like the Hellcat. So don’t miss your chance to drive one of the best – run, don’t walk, to your dealer now.