Image Credit: Ford.For decades, one of Ford's strangest Mustangs existed somewhere between an engineering prototype and an enthusiast legend. It looked like a fairly ordinary New Edge Mustang, yet hiding beneath its Cobra R-style hood was something Ford never offered Mustang buyers... A naturally aspirated V10.The car was built roughly 25 years ago as a one-off engineering project and never reached production. It survived, although years spent largely sitting meant the prototype eventually needed considerable attention if Ford wanted it to run properly again.According to Ford Heritage Fleet manager Matt Korczyk, his team recently reunited the Mustang with members of the original engineering group to bring it back to life. Electronics were replaced, and systems that hadn't received serious attention in decades were inspected and refreshed.AdvertisementAdvertisementThe goal wasn't to reinvent or substantially modify the prototype. Ford just wanted to preserve the car in working condition so another generation could experience what happened when a group of engineers decided to squeeze ten cylinders into a Mustang.Ford Built A 5.8-Liter V10 For ItThis isn't the 6.8-liter V10 Ford once installed in Super Duty trucks and other heavy-duty applications. Oh no, far from it! The Mustang's experimental 351-cubic-inch, or 5.8-liter, engine was actually developed from Ford's aluminum 4.6-liter Modular V8 architecture by adding another pair of cylinders.The resulting engine measured less than four inches longer than the V8. DOHC cylinder heads derived from the Cobra R helped turn it into something appropriate for a serious performance car rather than a truck engine.Making it work required some unconventional engineering. Ford didn't have a single production engine-control unit designed to operate the odd-firing V10, so the development team reportedly used two ECUs.AdvertisementAdvertisementPower travels through a T56 six-speed manual transmission to a nine-inch rear axle. The combination turned an otherwise familiar late-'90s Mustang shape into one of Ford's most fascinating experimental performance cars.The V10 Still Makes Serious Power[video width="1920" height="1080" mp4="https://guessingheadlights.com/wp-content/uploads/2026/09/main.mp4"][/video]Once the Heritage Fleet team was satisfied that the Mustang was healthy again, Ford put it on a chassis dyno. Korczyk described the run as the team's "report card" after bringing the long-dormant prototype back to operating condition.The result was over 510 horsepower at the wheels. Ford hasn't provided a corresponding crankshaft figure, but a fair estimate would place output around the 600 horsepower mark.AdvertisementAdvertisementThe number is particularly striking considering the era in which the Mustang was built. A regular 1999 Mustang GT's 4.6-liter V8 produced 260 horsepower at the crank, illustrating just how extreme Ford's experimental V10 project was at the time.The Original Engineers Came Back To See It RunImage Credit: Ford.The dyno session also turned into a reunion. Original team members Greg Coleman, Jim O'Neill, Paul Vella, Don Masch, Mike Shelby, and supervisor John Brune were present to watch the car they had developed decades earlier run again.Korczyk says those engineers originally spent nights and weekends machining parts, solving problems, and figuring out how to make the unusual V10 Mustang work. Seeing them reunited with the finished car ultimately became a bigger part of the occasion than its horsepower number.The Mustang apparently came close to disappearing at points during its quieter years. Enough people inside Ford recognized its significance, however, to ensure the one-off prototype survived.Ford Is Keeping Its V10 Mustang AliveFord never turned the V10 Mustang into a production model, and subsequent cars such as the Ford GT and Shelby GT500 eventually delivered similar or greater factory horsepower through different approaches. Still, that doesn't make this strange experiment any less fascinating 25 years later.AdvertisementAdvertisementThe Heritage Fleet's work means the prototype isn't destined to become a museum piece. Ford can still start it, drive it, and let that naturally aspirated V10 make the noise its original engineers intended. Preserving the Mustang is ultimately about preserving the people and ideas behind it.If you want more stories like this, follow Guessing Headlights on Yahoo so you don't miss what's coming next.