TOKYO — Nissan's GT-R may seem born and bred as a two-door car, but in truth the model started out back in 1969 as a four-door and had a two-door version added the following year. So, in adding a four-door GT-R, Nissan is actually going back to its roots.By adding the four-door, Nissan/Infiniti are hoping to tap into a wider customer base with a version of the supercar that offers more practicality, more luxury and betterride quality.Also to try to recover costs on such an expensive project as the GT-R's R&D, one Nissan engineer has hinted that certain parts including the platform and underpinningswill be employed in 'other models' and that its wheelbase will be stretched by 5.9 to 7.8 inches.It was initially rumored to get a slightly downtuned version of the GT-R's 480-horsepower twin-turbo V6, but one source close to Nissan says the company is now leaning toward a slightlytuned-up version of the 5.0-liter V8 that powers the Infiniti FX50. In that guise, the four-door GT-R should develop around 420 hp. The seven-speed automatic gearbox mated tothe FX's V8 will almost certainly migrate together with the 5.0-liter engine. Given that its main market will be the United States and that its main rivals will be the Porsche Panamera and the BMW M5, the V8 option makes sense.Other technologies expected to find their way onto the four-door GT-R read like a pack of alphabet soup. They include TPMS (tire pressure monitoring system with four-corner readout), ABS with EBD (electronic brake-force distribution), TCS (traction control system) with VDC (vehicle dynamic control), LDW (lane departure warning that beeps); LDP (lane departure prevention through selective brake application); and ICC (intelligent cruise control) with DCA (distance control assist) that maintains following distances at speed, plus IBA (intelligent brake assist) that will bring the car to a complete stop and then resume a selected speed automatically.The four-door GT-R is expected to weigh around 4,080 pounds and cost in the neighborhood of $100,000. It's slated for a late-2010 debut.Inside Line says: Four-door fans are about to get another great choice. — Peter Lyon, Correspondent