I would suggest the CX Racing Fan, Its pretty Slim, has good air Flow and its pretty cheap!
There 12' fan is only 2.5 inches thick
http://www.cxracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=CXR&Product_Code=RAD-FAN12&Category_Code=
The 14' fan is 3.2 inch thick.
http://www.cxracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=CXR&Product_Code=RAD-FAN14&Category_Code=
I would measure how much space you have between the IC Piping and the rad and go fro there.