If they're reference 6950s, it would be a good idea to grab full cover water blocks such as these:
And probably pick up an XPSC RS360 kit:
Maybe some extra tubing and fittings, etc. But I'd think that's a good bang for your buck solution to your issue.
If he doesn't have reference 6950s, check out these:
and these, to keep the VRMs cool:
I'm not the most knowledgeable about water cooling, but I've been recommended things like this. I'm not sure about mixing the elements (Nickel and Acrylic?) in a loop, so I'll leave that up to other people. There are multiple versions of most of these products in different elements, so keep that in mind.
Best of luck! Hope this helps.