[Azriel]

Alternatively, I could put two high CFM 80mm fans in the front fan location, and just shroud the heater core and the pump in with them.

Either way, I want to keep the core and the pump inside a box. If I drilled pin holes in the four corners of this area, I'd know about a leak from either before the floor of my case was full of water. I think I'm am also going to go with a simple externally mounted reservoir so a level drop will be obvious.