Porsche has created a road-legal version of its successful 963 endurance racer, rekindling the spirit of a road-going Le Mans legend it built 50 years ago. 

The 963 RSP is inspired by, and specified to match, the road-legal version of the legendary 917 that Porsche built for Italian aristocrat Count Gregorio Rossi di Montelera in 1975. 

Like that car, which still appears regularly at events like the Festival of Speed and Villa d'Este, the road-legal 963 is all but technically identical to its racing counterpart, which will go for glory at Le Mans next week.

Porsche's LMDh hypercar – which competes in the same World Endurance Championship (WEC) class as the Ferrari 499, Alpine A424 and BMW M Hybrid V8 – is based on an LMP2-spec chassis made by Canada's Multimatic. 

However, its 671bhp hybrid drivetrain is centred around a thumping 4.6-litre twin-turbo V8 derived from the old Porsche 918 Spyder hypercar. 

Porsche hasn't revealed performance figures, but taking into account the 963 racer’s estimated 0-62mph time of around 3.0sec and a top speed of more than 205mph, the 963 RSP should be one of the fastest Porsches yet to wear a numberplate. 

As well as competing in the WEC, the 963 is a regular fixture at the top of the standings in America's IMSA Sportscar Championship, in which it is fielded by Porsche's motorsport partner Penske - the owner of which, Roger Searle Penske, has commissioned the road-going car, hence its 'RSP' moniker.

Rather than being adapted from an ex-race car, the 963 RSP was built from the off for road use by the US division of Porsche's Sonderwunsch bespoke arm, based in Atlanta - and it has proven its cross-country credentials by driving on the roads around Le Mans ahead of next week’s 24-hour race.

To ensure it can be driven on the road, Porsche has fitted the 963 RSP with indicators and brake lights, put the suspension in its highest setting, fitted less extreme wet-weather tyres and subtly reworked some of the more track-focused bodywork. The vents on the front wings, for example, have been covered so that the wheels don’t throw stones back at the windscreen. 

It also has a cupholder fitted, to compensate for the removal of the button-activated drinks system that hydrates the 963’s drivers during a race. 

Sonderwunsch has worked to closely match the specification of Rossi’s car, down to the tan interior and ‘Martini’ silver paint, which was a particular challenge to apply, due to the 963 being completely carbonfibre-bodied.

Despite being road-legal in certain countries, the 963 RSP does still need a laptop to start - unlike Rossi’s 917, which had a very conventional ignition key. 

Porsche will show off the 963 RSP on the sidelines of La Sarthe next week before bringing the car to the UK in July for the Goodwood Festival of Speed. 

It has told Autocar that the car – understood to have cost in the region of €5 million – is a one-off for now but that it wouldn't rule out building another if approached.