The word "unique" gets thrown around a lot, but it definitely applies to The Beast, which packs a 27.0-liter Rolls-Royce Merlin V-12 aircraft engine into a custom chassis and body. Built by British mechanic John Dodd, it's being auctioned off online by Car and Classic. Bidding opens March 9.

Aircraft engine swaps had been done before, especially during the prewar period, but the The Beast took things to another level by harnessing the legendary Merlin. Developed by Rolls-Royce, but also manufactured under license in the U.S. by Packard, it powered some of the most successful World War II fighter planes, including the Superman Spitfire and North American P-51 Mustang.

The naturally aspirated engine is thought to produce 750 hp, which the listing notes is reasonable considering that production versions of the Meteor engine were rated at 1,500 hp with a supercharger. Dodd also once claimed 950 hp and 760 lb-ft of torque. A transmission specialist by trade, he also modified a General Motors Turbo 400 3-speed automatic to work with the massive V-12. It originally sent power to a Jaguar rear axle, but a sturdier Currie unit now handles the power.

The Beast is no longer the only Merlin-powered car around. Jay Leno has a 1934 Rolls-Royce powered the historic engine, estimated to make about 1,000 hp and 1,750 lb-ft. But while Leno's car has never been top-speed tested, The Beast reached 183 mph in a 1973 Royal Automobile Club (RAC) test.

The Beast's story starts in 1966 when Paul Jameson constructed the frame and sourced a variant of the Merlin engine called the Meteor that was designed for use in tanks. He never finished the project, eventually selling the engine and chassis to Dodd, who completed it with a fiberglass body in 1972.

The car was damaged in a fire at one point, after which the original engine was replaced with a new one of identical spec, and the original body was replaced with the current shooting-brake version.

The Beast once had a Rolls-Royce grille in homage to the engine, something that didn't amuse the company, according to the auction listing. Rolls sued and won, although Dodd reportedly didn't change the grille until a few years after the lawsuit concluded. The car is listed as a Rolls-Royce on its U.K. registration, however.

The car has had four owners over the years, all thought to be members of Dodd's family. The listing claims it's still in running condition, although where anyone would drive this aptly named creation is unclear.