There's a ton of blocks out there. I'd suggest checking out ekwb.com. Use their cooling config tool http://www.coolingconfigurator.com/
to decide which works for your card and looks good. A single 120mm fan is good enough to cool the Vrams so 2 for both cards is ditto. If you have a case that can blow air directly to the cards like a switch 810/air 540, that would be great.
Another option would be to get this http://www.overclock.net/t/1221722/sigma-cool-aio-gpu-mounts-mount-kuhler-620-nzxt-kraken-x40-on-your-gpu-ship-same-day/450
. This is cheaper but won't be as neat as getting a universal waterblock and integrating it into your current loop; if you have one. It's very effective and I think I might go that route myself.
There's a fan mounting kit I remember someone posting here a while back that is very effective at cooling gpus and easy to use. I'll post it when I find it.