I don't know. You might be able to route it like the attached picture, but I'm not totaly sure. You would have to change the water pump pulley to a ribbed pulley. There wouldn't be much contact area from the belt to the water pump pulley (although it would need far less than the backside as the ribs have more surface area). And I don't know if the tensioner would extend far enough to tension the setup.

You might try giving Chuck Jones of Jones Racing Products a call. He specializes in accessory drive. He's done just about everything and I'm sure he can give you a pulley combination that will work.

http://www.jonesracingproducts.com/