Genuine road-going Le Mans hypercars are vanishingly rare, unless you’re Porsche. From the Dauer 962 Le Mans and 911 GT1 Straßenversion to today’s 963 RSP, Stuttgart has made a habit of bringing La Sarthe to the road. This latest creation is a one-off, street-legal version of their top-class prototype.

Built in tribute to 917 Chassis 30, the colour and trim are heavily inspired by the specification and spirit of Count Rossi’s request for a true racer for the streets, a trackside conversation between Porsche officials turned into a painstaking project involving the motorsport and classic divisions.

In order to make the car road-legal, the ride height has been raised to its tallest position, and the Multimatic DSSV racing dampers are in their softest setting to provide a relatively compliant ride – at least by prototype standards. The wheel arches have been redesigned to incorporate new air vents, and the carbon blanking plates required for competition have been removed. Porsche has even gone as far as reprogramming the headlight control unit to make the LED projectors suitable for driving at night.

The RSP is the only 963 to feature painted bodywork as opposed to vinyl wraps. The finish is precisely colour-matched to the Martini Silver 917 of Count Rossi, and an enamel Porsche badge features on the nose. Beneath the matte black sharkfin lies the car’s powertrain, with a 4.6-litre V8 derived from the 918 Spyder. The engine has been reconfigured to run on non-racing fuel, and uses a pair of hot-vee turbochargers to send 671bhp to the rear wheels through an Xtrac 7-speed sequential gearbox. The bell housing contains the Bosch electric motor which is common across all cars built to LMDh specifications.

The hybrid system has been tweaked to provide smoother power delivery, while still being able to run the car solely on electric power. The Williams Advanced Engineering-supplied 1.35kWh capacity battery runs at 800 volts, and can deploy its power from a standstill to its top speed. Consistent with the racing variant, activation of the 67bhp electric motor causes the engine to reduce its output, so as not to exceed the regulation-mandated 671bhp maximum.

The 963 RSP features a hand-crafted leather and Alcantara interior, complete with an air conditioned seat. Almost every surface – save for the dashboard – carries the tan hue of the 917 Chassis 30. Although Le Mans Prototypes are designed with two-seat cabins by regulation, the right-hand side features a leather shelf on which to place a laptop. Rather than allowing the owner to dial into conference calls that could’ve been emails, it’s where the computer required to start the 963 RSP can be rested.

Usability has been considered as part of the project, as the bespoke Peltor headset has its own dedicated hook, and a 3D-printed cupholder designed to fit a Porsche travel mug features in the centre of the cockpit. Aiding visibility is a digital rear-view mirror which takes a live feed from a roof-mounted camera. Further references to the 917 are subtly placed in plain sight, with the air vents designed to look like that car’s cooling fan, and 1970s Michelin branding on the tyre sidewalls.

The result of the project is a car as close to race-spec as possible, that can be driven on the road with special permission. The number plate-equipped 963 RSP took to the streets that will soon host this year’s edition of the 24 Hours of Le Mans, with two-time winner Timo Bernhard at the wheel, and the 917 Chassis 30 in tow. However, don’t expect it to become a common sight in traffic. The car is described as “not a homologated addition to the Porsche model line-up and is intended to remain a very special one-off.”

After Le Mans, the 963 RSP will appear at the Goodwood Festival of Speed in July and will likely spend most of its life in its owner's private collection. The “RSP” designation is a tribute to Roger S. Penske, the owner of Team Penske and the driving force behind Porsche’s championship-winning efforts in both the IMSA and WEC series.