So, I've actually done this, except instead of getting the $25 copper water block, I got the $5 aluminum version...
https://www.amazon.com/Oxidation-Cooling-Block-Computer-semiconductor/dp/B01MECPBSO/ref=sr_1_11?s=pc&ie=UTF8&qid=1479701477&sr=1-11&keywords=water+block
I also used that exact water pump haha.
I used an old oil cooler radiator with a fan tied onto it and had it in a bucket on the floor to use as the reservoir / drop catcher because I didn't seal the connection to the radiator, then I just had the pump in the bucket because its submersible.
As a bonus, because it was winter in canada I could supercharge the cooling with snow as long as I was careful not to get it to the point where condensation would be an issue...
I've taken it apart since because it was so janky though obviously...