I wouldn't run ducts from the louvers to the fan, as Tom is considering.
If you compute the volume of air that the fan is moving, you'll find that
it is changing the air in the engine compartment pretty fast, and the
possible result of ducting is that it gets in the way.  The only special
ducting VW did was on Vanagons to bring unstinky air into the passenger
heating system.

People with race experience have told me that if I put "ears" at the rear
of my intake louvers (81 Vgon) to bring in more air I will see 10oF. lower
temperatures at highway speeds.  I might even try this since on 81-> Vgons
it can be done without touching the sheetmetal, just modifying the louvers.
B.
Wm Kennedy
kennedy@admin.njit.edu