Ford has brought its one-off V10 Mustang prototype back to life 25 years later. Its naturally aspirated 5.8-liter V10 now makes more than 510 hp at the wheels. The experimental engine was essentially a 4.6L Modular V8 stretched by 2 cylinders. Ford has built plenty of strange Mustangs over the past six decades, but few can touch the glorious absurdity of this one. It looks like a mildly modified 1999 Mustang GT, yet underneath that Cobra R hood sits a naturally aspirated 5.8-liter V10 that Ford never put into production. For years, the one-off prototype largely sat out of sight, occasionally getting dangerously close to disappearing altogether. More: Ford Shelby Cobra Concept Sells For $2.64 Million At Monterey Car Week Photos: Ford Now Ford has brought it back to life. And apparently, the old pony has been hitting the gym. The Ford Heritage Fleet recently worked with members of the original engineering team to recommission the car, replacing electronics and going through systems that hadn’t received much attention in decades. Once everything was working properly, there was really only one sensible thing left to do, and that’s to strap it to a dyno. It laid down more than 510 horsepower at the wheels. The Prototype Wakes Up Angry That’s probably around 600 hp (447 kW) to the crank and considerably more than the car produced when it was making headlines two decades ago. Contemporary testing reported 426 hp at the wheels and 400 lb-ft (542 Nm) of torque. It also ran the quarter mile in as little as 11.93 seconds at 117 mph (188 km/h). It’s unclear where the power bump comes from, but it does appear as though there’s a modernized intake on the car now. That alone could make for some solid gains. Still, the engine itself is arguably more interesting than the numbers. Back when Ford’s team put this together, it was already making a V10. In fact, it was an even larger 6.8-liter unit built for trucks. That engine and the one in this Mustang aren’t really related beyond their brand name. The experimental 351-cubic-inch (5.8-liter) unit was essentially Ford’s aluminum 4.6-liter Modular architecture stretched by two cylinders, complete with DOHC heads derived from the Cobra R. Photos: Ford That made it less than four inches (100 mm) longer than the V8. The team had to use two ECUs because Ford didn’t make one that could control the odd-firing V10. To round things out, a T56 six-speed manual sends power to a 9-inch rear axle. Despite never making it to production, Ford has kept the car and clearly cared enough to restore it for future generations to enjoy. Perhaps the best part is that nobody has to explain to accounting why they’re building it this time. Photos: Ford