I have run universal blocks exclusively since 2005 because I tend to reuse them. Actually, I have a DD Maze4 Acetal from 2005 running on one of my 7950s right now. Of course, because the core was rotated, I had to grind down portions to make it fit but it works perfectly well. However, since I modded it, this will be the last card I use it on.
As the poster above mentioned, you should know what you need to cool.
The easiest solution I find is to get a non-reference card that has a separate cooler/plate for the VRAM and VRMs, and one where you can attach a universal block without removing those, and then just point a fan at it. This is how I run my MSI TF3 7950 and an XFX DD 290.