Well I'd take a different route.. I'd try and make sure that your cooling system runs at maximum efficiency first. Maybe get it flushed, and put in some new/clean coolant. Also spray out your radiator to get all the nasty old bugs, and dirt and grime out.
Read these articles posted by Killerbee...
Performance, Intakes, Thermal Feedback, LLY Mouthpiece
They deal with the LLY motor, but it can be applied to all duramax's.
The most effictive way to actually help keep your engine cool would be to add an auxillary engine oil cooler. If you read those three articles posted by Killerbee you'll know more than some GM diesel techs do!!
Edit: The third article is titled "Thermal Feedback Loops" and is a link in Killerbee's signature.