SPY PICS: Mystery Ford Mustang Shelby GT500 prototype hides a roll cage

A mystery Ford Mustang Shelby GT500 prototype has just been spotted cruising through Dearborn (Michigan) wearing manufacturer plates and some heavy-duty camouflage over its rear-end.

There are two main possibilities here, the first being that the spied vehicle is an early test mule for the new S650-generation GT500 due in 2025 – the development and production timeline would certainly line-up.

The other working theory is that this is a swansong GT500 based on the outgoing S550 Mustang, designed to help get remaining stock and/or componentry out the door in preparation for the next-generation supercharged monster.

Both theories are entirely plausible, but the images would tentatively suggest the latter as the more likely option given the camouflage is only covering the boot lid and rear window.

Hiding under the obscured rear glass is a full roll cage, while the boot lid is thought to be adorned with some sort of revised spoiler – one of the key factors in the swansong theory.

The really interesting thing, however, is the fact that beyond the roll cage and exterior camo, the Shelby is in complete production specification with all of its exterior trim bits, red-painted brake callipers, aero kit and paint finish.

Besides the camo and industry plate, only the rough looking 10-spoke alloys and sensor taped to the roof betray the vehicle as a prototype of some description, while the roll cage suggests this Shelby could be even hotter than the standard GT500 that outputs a mighty 566kW/847Nm courtesy of its supercharged 5.2-litre V8.

If we were to hazard a guess as to what exactly this prototype is – provided it’s an S550 variant – we’d say it’s a road-going derivative of the ballistic, track-only GT500 Code Red that was shown off this time last year.

The Code Red swapped out the standard car’s supercharger and replaced it with a pair of turbochargers backed by new fuel and engine management systems to develop up to a mammoth 969kW/1355Nm when running on E85.

Just 30 examples of the drag strip special were/are being made and it stands to reason that a detuned road-going version – intended to run on more readily available 93-octane fuel – would make one hell of a send-off for the current-generation Shelby portfolio.

The Code Red roars out 745kW/1058Nm on 93 RON, which could explain why this new prototype is fitted with a roll cage.

“While not street legal, it’s very capable at moderate speeds in most any curve. But when the turbos spool up, the car is best enjoyed moving straight ahead,” Shelby American R&D boss Vince LaViolette said of the Code Red.

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