Isuzu had previously been active in touring car and special touring car classes with factory-supported vehicles but had consistently ignored the main event—the Japanese Grand Prix. However, this year, following the company’s recent surge of interest in sports cars, they suddenly entered the GP with four machines, two of different sizes.

From the start, winning was nearly impossible, and given that the entire project had only begun five months earlier, even securing a high placement was an unlikely goal. However, as long as they continue putting in the effort, the time will surely come when they can compete for victory. In that sense, there are high expectations for Isuzu’s prototype efforts in the future.

Among the two types of cars, Isuzu’s primary focus was on the smaller Bellett R6. This car featured a production-based 117 engine mounted in a newly designed mid-engine chassis-body structure. It could be considered a pilot model for Isuzu’s new mid-engine GT, which was set to debut at the Tokyo Motor Show that fall (internally, Isuzu referred to the R6 as "142," while the show car was designated "143," reflecting their connection).

The body shape of the R6 was reminiscent of the Porsche 906, Nissan R380, and Daihatsu P5, and its technical level did not significantly surpass that of those competitors. According to the manufacturer, the engine utilized many components from the production 117 model, including a steel block, aluminum head, connecting rods, and crankshaft, all sourced from the production line. Consequently, it was a 1,584cc, DOHC, 2-valve, 4-cylinder engine with a bank angle of approximately 60°, driven by a chain. To lower the engine’s position, it was converted to a dry-sump system, while intake and exhaust systems were refined, and the jet diameter of the twin-choke Solex carburetors was increased for overall tuning. The ignition system was transistor-based. While the production 117 engine produced 120 HP at 6,400 rpm, the R6 was estimated to output around 150 HP at 7,000–7,500 rpm. The gearbox was a 5-speed, non-synchronized Hewland unit designed for Formula 2 and Formula 3 use.

The chassis was a completely original design. From the scuttle rearward, it featured a fabricated steel semi-monocoque structure similar to Can-Am machines. A tubular space-frame subframe extended forward to mount the suspension, while at the rear, box-section side rails and steel tubes extended to support a loop-shaped bulkhead surrounding the differential and rear engine mount. It appeared extremely sturdy, though despite weight-saving holes, it still looked quite heavy.

The suspension followed the standard layout of contemporary racing machines: double-wishbone with coil springs at the front and a four-link coil-spring setup at the rear. The half-shafts featured two universal joints on each side with a sliding spline in between. Torsion-bar stabilizers were installed at both the front and rear. The rack-and-pinion steering system and steering knuckles were sourced from the Bellett, while the dampers were manufactured by Showa Seisakusho. The brakes were Girling solid discs mounted outboard on all four wheels. The 15-inch magnesium wheels were initially fitted with Firestone rain tires during practice but switched to Dunlops for the race.

The FRP body mounted on a 2.3m wheelbase chassis was designed as a coupe in accordance with Group 6 regulations. It featured headlights in the nose, a regulation-compliant windshield, and gull-wing doors. The fuel tank, initially designed to meet the 100L regulation, was planned to be enlarged for group races but could not be modified in time. The oil cooler was positioned at the front of the car, while the main radiators were housed inside the rear fenders.

The design weight was reportedly 630 kg, but in reality, it was slightly heavier. Assuming a weight of 630 kg and an estimated 150 HP output, the power-to-weight ratio would be around 4.2 kg/HP. During practice, driver Yonemura encountered bearing failure, necessitating an emergency engine swap. Unfortunately, both cars experienced repeated mechanical troubles in the actual race, preventing them from achieving their intended performance, which was a disappointment.