try putting a few smaller washers where the fan mounts to the clutch, just make sure you mount it securely.. if that doesn't work (dunno why it wouldn't), then you could try shaving some material off the back of the blades like Bigzavs and some other have done.
regardless of how much spacing occurs, the clearance (in regards to the water neck) is never gonna be as good as say the GTE fan blade IMO.. though as previously stated, the GE blade allows one to retain the clutch fan setup if going to a bigger rad.