Here I posted my initial design for an Ati All-in-Wonder 9700 Pro water cooling solution... you can use it however you wish.
I'm only in it for the fun.
Tweak the passage layout however you like as I'm still revising them, and, yes that's a #Rotor design over the GPU core.
The base measurements for the card itself are
here.
When I get everything revised I will probably repost here with pictures of me machining this on my home mill.
(Small mill but effective

)
Good luck with your cooling endeavors!