first of all the word 'investing' probably isn't the right word to use when buying a car
As for the km's, ignore them, they don't mean anything, 99% of imports are wound back and made up log books etc.
Look at the condition of the car. Look for common wear marks. If it really has 40,000ks then the car will look brand new, there probably wouldn't be a mark on the interior and it should still have that new car smell
Look for wear on the steering wheel, the gearstick boot, the gear knob, the seats, the indicator stalk, the pedals, etc...
Get it checked out by someone familiar with GTR's.