The Thermaltake 1U P4 heatsink would make an excellent base if it was 'carefully' crosscut to pins instead of fins, MUCH more dense 'finage' surface area for cooling. Those pins look to far spaced to me

. I'd have them a little lower as well, will heat travel all the way up them?, it'd boost H2o pressure if it was lower as well...
With the pin base you have I'd drill loads of shallow holes in the surface as well to add to the turbulance/area...
Booteful

job as allways though Bladerunner!...
PS, LINK to
1U P4 HSF @
theoverclockingstore.co.uk ...
Volenti has posted some threads where he modded one for H2o use, they are an excellent base!...