Image Credit: Autotopia LA / YouTube.At first glance, this 1989 Ford Mustang GT looks like an exceptionally clean Foxbody wearing a tasteful set of wheels. The white bodywork is almost completely stock, and there are few obvious clues that anything particularly serious is hiding underneath.Autotopia LA recently got behind the wheel of the Roadster Shop build, revealing just how deceptive that appearance really is. The build is based on an incredibly low-mileage example with only around 3,500 original miles, and Roadster Shop chose to preserve its factory look rather than turn it into an overtly modified showpiece.The exterior still resembles the kind of Mustang GT you might have seen cruising around in 1989, and the interior also retains much of its original character.AdvertisementAdvertisementUnder the surface, however, virtually everything that truly matters has been transformed, as this familiar-looking Foxbody now packs an 800-horsepower naturally aspirated V8, a modernized chassis, and the ability to rev to a staggering 8,800 rpm.Its Naturally Aspirated V8 Makes Around 800 HPImage Credit: Autotopia LA / YouTube.Rather than taking the increasingly familiar Coyote-swap route, Roadster Shop worked with Wegner Motorsports to create something considerably more unusual. The result is a 434-cubic-inch, or roughly 7.1-liter, naturally aspirated small-block Ford based around a Dart Windsor block.D3 NASCAR cylinder heads sit on top, accompanied by titanium valves, billet shaft rockers, and custom components, including the intake and valve covers. There's also a Daily Engineering billet dry-sump system, while the engine reportedly produces around 800 horsepower on pump gas and can spin all the way to 8,800 rpm.Two-inch primary 180-degree headers give the engine an appropriately exotic soundtrack. Power reaches the rear wheels through a Bowler T-56 six-speed manual, carbon-fiber driveshaft, and Ford nine-inch rear end with 3.90 gears and a Wavetrac limited-slip differential.There's An Entirely Different Chassis UnderneathImage Credit: Autotopia LA / YouTube.The engine is only part of the transformation, because this Mustang became the first car fitted with Roadster Shop's bolt-on Foxbody chassis, which runs from the front bumper to the rear and is designed to attach to the original unibody.AdvertisementAdvertisementElectronically controlled coilovers can operate in passive or adaptive modes, with comfort, sport, and race settings available. In adaptive operation, the system can alter damping response as the car accelerates, brakes, and corners.Braking comes from Baer hardware with a custom billet pedal assembly and manual brakes, while an adjustable electro-hydraulic power-steering system lets the driver change assistance. Roadster Shop also fitted C7-style sealed rear hub bearings and floating hubs to better cope with hard driving.The understated HRE wheels measure 18x9.5 inches up front and 18x12 at the rear. They wear 255/35 front and enormous 335/30 rear tires, giving away some of the Mustang's intentions without dramatically changing its period appearance.Even The Interior Tries To Look OriginalImage Credit: Autotopia LA / YouTube.Roadster Shop applied the same philosophy inside, and the original seats are still in place because the low-mileage upholstery was in exceptional condition, while the factory steering wheel has been kept for now.AdvertisementAdvertisementLook more closely, and modern equipment starts appearing. Dakota Digital RTX instruments mimic the original gauges, Vintage Air provides modern climate control, and a retro-looking Blaupunkt head unit hides Bluetooth and contemporary audio functionality behind its period appearance.Image Credit: Autotopia LA / YouTube.There's considerably more hidden in the rear, including two eight-inch subwoofers, Focal Utopia audio equipment, and Mosconi electronics. A four-point cage and harnesses add some useful restraint when the V8's 800 ponies are being exercised properly.It Drives Nothing Like A Stock FoxbodyAutotopia LA's road test suggests Roadster Shop achieved exactly what it intended. Despite maintaining so much of the original Mustang's visual identity, the chassis eliminates the loose, flexible character commonly associated with an old Foxbody, and the naturally aspirated engine offers immediate and predictable response.Unlike most restomods, Roadster Shop didn't need to redesign the Foxbody to make it special. Instead, they simply hid an 8,800-rpm, NASCAR-headed monster underneath one.AdvertisementAdvertisementRoadster Shop also stressed that development wasn't completely finished, with further suspension and throttle tuning planned, which means it'll soon be even better than in its current state.If you want more stories like this, follow Guessing Headlights on Yahoo so you don't miss what's coming next.