The distance is around 350mm.
But it is to be ducted as well with a shroud that fits with a rubber seal against the back face of the radiator.
And the hood opening will seal against the top edge of this shroud.
The shroud will contain two fans.
So the shroud becomes an adaptor between the radiator & hood.
It is designed so the radiator seals with rubber against the front of the bodywork.
So all the air that enters the grill must go through the radiator, then through the shroud & up out of the hood.
The air flow through all of these parts flows very clean with no obstructions.