Right you are!
I do not really know how you´ve managed to identify this, but it is indeed an 2l G6 Isuzu racing car.
I´m not totally sure about its model designation, but I think it is "Isuzu Spider 2000" and it ran at the 1973 Fuji 300km as I can recall from my memory.
I´ll check these dat when I´ll be back from work.
But this is definitly your point!