7 classics with so much horsepower, you'll know why they're called 'muscle' cars

When maneuvering, cornering and handling take a back seat to raw, unadulterated power, you can't go wrong with the beefiest muscle cars on the planet. 
Here we've compiled a list of seven classic muscle cars that have become the stuff of legend, all sporting incredible engines and gorgeous looks, built at a time where the pursuit for more and more automotive grunt was never ending.
1. 1965 Shelby Cobra 427 Roadster
Offering somewhere between 400 and 500 hp, the 1965 Shelby Cobra 427 Roadster was built in very low numbers, and according to SuperCars, these days an example will fetch over $1.5 million.
2. 1969 Ford Mustang Mach 1 Fastback
According to Caranddriver, the Ford Mustang Mach 1 with a Ramair Cobra Jet & Super Cobra Jet V8 was conservatively rated at 335 hp. The original "pony car", the Mach 1 saw four further generations before being retired in 2004. Rumors abound of a return of the Mach 1 in 2018.
3. 1970 Buick Gran Sport Stage 1
Long-term rival to the Chevrolet Hemi (listed below) for the throne of muscle car power, tests on a model in 2004 show the Buick Gran Sport actually offered between 360 and 382 hp. According to Wikipedia, the powerful engine can cause overheating of the A-arm bushings, leading to rapid tire wear and problems with front end alignment.
4. 1969 Chevrolet Camaro ZL1
Only 69 of the original ZL1s were ever built. With the high 1969 price tag of $7,200, only 13 of the first 52 could be sold, the rest being sent back to Chevrolet from the dealership, according to Jalopnik. However, the reputation of the ZL1 for being the one of the fastest performance cars ever built (easily 500 hp), coupled with its rarity, have seen the ZL1 sell for almost half a million dollars.
5. 1968 Plymouth Hemi Barracuda
Conservatively rated at 500 hp for insurance purposes, the 1968 Plymouth Barracuda with Super Stock 426 Hemi offered well over 600 hp, according to MyClassicGarage. It's still one of the fastest cars in the world, capable of flying a quarter mile in 8.30 seconds at speeds of up to 160 mph.
6. 1964 Ford Fairline Thunderbolt
Due to laws at the time, the Ford Fairlane Thunderbolt was listed as 425 hp to get around some red tape. Unofficially, this street legal beast throws out something between 500 and 600 hp.
7. 1964 Ford Galaxie 427 SOHC
The overhead 427 V8 engine is arguably Ford's best ever engine, and in the 1960s it was banned from NASCAR after Chrysler rightly predicted it'd destroy their 426 Hemi on the track. However, a rare few of these 660-hp engines saw their way into Ford Galaxies and were shipped out to customers as "prototypes".