Great! Post how you did it (include things like did you remove the old compound from the chips, what you put on, screw torque amounts, etc) so other people can do this as well.
The Ebay coolers are a bargain....
Would I be able to take the pumps off a working 400mhs Unit and install them on a 700mhs?
Probably. I did this once to test the problematic 700mhs unit I had, prior to getting the new units. I was never able to figure out the 700 unit I had that was hashing at 400 - 460. It wasn't cooling or power.
These units are very interesting. I'm impressed that BFL was able to produce such a decent unit (albeit hot-running and below performance expectations) given all of their failings.