I love to see DIY mods...keep us updated. Sorry that I don't have the info for you off-hand, but I want to see what comes of this project.
(Thinking of PS3 watercooling mods since they really don't have any blocks for the Slim...this could be a possibility outside of finding universal blocks to work.)
Edit: Here is what I found on the Corsair FAQ page:
What are the dimensions of the pump/CPU block on the H70?