As a sub-brand of Ford, Mercury enjoyed access to a wide range of parts, chassis', and engines from the American automaker. During the 1970s, the brand made great use of this exciting privilege and turned out some impressive and desirable muscle cars.While many of them sold well, some failed to capture the interest of the American public and barely managed to shift more than a few dozen. One trim in particular though, in 1972, only managed to sell just one example. Its whereabouts are currently unknown, but that just adds to the mysterious appeal of this unique Mercury muscle car. The 1972 Montego Cyclone Is The Rarest Mercury Muscle Car Ever Produced MecumMercury launched the Montego in 1968, positioning it as a more refined, midsize counterpart to the Ford Torino. After three years in its original form, the model received a complete overhaul for 1972, ushering in its second generation with a variety of body configurations and trim levels. Among these offerings, the GT and MX variants proved most sought-after by buyers. While these two models shared fundamental design DNA, they diverged in their rooflines—the GT featured an aggressive fastback profile that swept dramatically rearward, while the MX adopted a more traditional notchback silhouette.Mecum Performance enthusiasts could opt for the Cyclone package, which had previously existed as a standalone model before being integrated into the Montego lineup. This performance-oriented option bundled numerous enhancements and gave buyers access to two formidable powerplants from Ford's muscle car arsenal: a 351-cubic-inch Cobra-Jet V8 producing 248 horsepower, or a larger-displacement 429-cubic-inch V8 generating 208 horsepower. Either choice represented a substantial leap beyond the GT's standard 302 V8, which mustered a modest 140 horsepower. Only One Mercury Montego MX Cyclone Was Produced In 1972 Mecum While other models within the larger Ford umbrella were selling in huge numbers, the second-generation Montego was struggling to capture such success. As a result, sales figures were low across the whole range, with the high-performance Cyclone trims being hit the hardest. According to figures obtained by Hemmings via the 1972/73 Mercury Montego GT Registry, just 29 Montego GT Cyclones were sold throughout the whole of 1972. Of these, 20 were specified with the 429ci V8, and only 9 with the Cobra-Jet engine.Those production numbers are low enough to make the Montego GT Cyclone one of the rarest muscle cars ever produced by Mercury, but the title of rarest overall belongs to an MX model. As, for 1972, just one Montego MX was specified with the Cyclone package, and that owner had opted for the impressive Cobra-Jet V8. This true one-off is, by some margin, the rarest Mercury muscle car ever produced. Here's What Makes The One-Off 1972 Montego MX Cyclone Special Mecum True to the muscle car ethos of the 1970s, the Montego Cyclone package extended well beyond mere horsepower figures. Mercury understood that buyers investing in a performance model expected visible proof of their purchase—enhancements that announced their car's pedigree from every angle.The exterior transformation began with an aggressive hood scoop emblazoned with 'Ram Air' graphics, serving as the Cyclone's most commanding visual signature. Mercury further distinguished these models through distinctive striping schemes, prominent Cyclone badging across the bodywork, and dual racing mirrors that added both style and functionality. Inside the cabin, drivers gripped a sporty three-spoke steering wheel that reinforced the performance-focused character.Beneath the sheet metal, the differences continued. Standard Cyclone models rolled on F7-14 tires mounted to wheels dressed with hubcaps and trim rings, providing adequate grip for the Cobra-Jet's output. However, the more powerful 429-cubic-inch variants received upgraded G70-14 rubber as standard equipment—though Cobra-Jet buyers could opt for these wider tires as well. Transmission choices varied by engine: every 429ci Cyclone, whether GT or MX bodystyle, came exclusively with a four-speed automatic. Cobra-Jet customers enjoyed greater flexibility, choosing between the three-speed automatic or a four-speed manual gearbox to suit their driving preferences. The Whereabouts Of This Unique Mercury Muscle Car Are Unknown While many rare muscle cars, and even one-of-one muscle cars, much like the '72 Montego MX Cyclone, still exist and are cherished by lucky collectors today, the location of Mercury's muscle car is sadly a mystery. If discovered, it would no doubt be one of the best barn finds of the decade, but the probability is that it was scrapped or broken a long time ago. Such was the fate of many '70s models from Mercury. A Closer Look At Mercury's 351CJ Cyclone Engine Mecum Mercury never intended the Montego, which followed on from earlier Cyclone GT models, to be a real big player in the muscle car world. That would make no sense, as it would tread all over the toes of Ford's hottest models. Still, with a 351ci Cobra-Jet V8 under the hood, it certainly had enough bite to match its bark.Power came in the form of 248 all-American horses, while torque was impressive too, at 299 lb-ft. Humble figures by today's standards, but back in the early 1970s, that sort of grunt was more than enough to guarantee plenty of smiles per gallon. The Cobra-Jet engine went on to power a wide number of Ford cars and is considered one of the best muscle car engines of the period. Engine Specs Here's How Much A 1972 Mercury Montego Muscle Car Will Cost You MecumThe valuation given by Hagerty is for a Montego GT, equipped with the 351ci Cobra-Jet V8 – a package that would've cost an additional $518.10 on top of the GT's asking price, back in 1972. Hagerty does not list values for the one-of-one MX Cyclone, naturally, as it's such a rare car, and its existence is not even certain anymore.Even so, the '72 GT Cyclone with a 351ci Cobra-Jet is still a wildly scarce car, with just nine in circulation from new, so it's surprising to see that even a concours one won't set you back much more than $24,000, which makes this Mercury a hot and properly affordable classic. We'd assume the unique MX model would fetch more if it ever surfaced, purely due to its obscurity, but we may never know for sure. 1972 Mercury Montego GT Cyclone Valuation Table