After returning to sports car racing in 1995, Nismo had some measure of success with their Skyline GT-R LMs which had competed in the GT1 class. However, these cars were quickly outpaced by the influx of new manufacturers who were using loopholes in the GT regulations to build racing cars that bore little resemblance to their GT1 class competitors. This led to such machines as the Mercedes-Benz CLK GTR and Porsche 911 GT1, as well as the development of the McLaren F1 GTR. Nismo's Skyline GT-Rs therefore needed to be replaced with more purpose built machinery.
Turning to Tom Walkinshaw Racing (TWR), Nismo began development of the R390 GT1, named to follow in the tradition started in the 1960s with Nissan's R380. The first decision for Nismo and TWR was the choice of engine. The previous Skyline GT-R LMs had used the trusted RB26DETT Inline-6 motor, but the design was old for a racing car, employing an iron block which added weight. Nismo instead chose to resurrect an engine from the Nissan R89C, a racing car from the Group C era. Its engine, the VRH35Z, was a 3.5L V8 which used an aluminium block, as well as having a lower center of gravity and a better ability to be used as a stressed member over the RB26. Thus the engine was upgraded and designated VRH35L, and would produce approximately 641 hp (478 kW) at 6800 rpm.
The car's styling group was led by Tony Southgate, a member of Tom Walkinshaw Racing and the designer of the Jaguar XJR-9 which had won at Le Mans. Due to this, the R390 GT1 bears a resemblance to the Jaguar XJR-15, which was also developed by TWR and based on the XJR-9. Development of the car was achieved in a small amount of time, especially due to not having to scratch-build an engine. Nismo and TWR also had to build a production version of the R390 GT1 in order to meet production regulations. Only two road-legal R390's were built, with one road car ending up in storage at Nissan's Zama, Kanagawa facility.
For 1998 the R390 was modified, most notably in the extension of its rear bodywork to create more downforce naturally, thus creating a "long tail" version.
Source by Wikipedia