Not sure if this is relivent to your wants but it doesnt hurt to post this message
Have you seen the Alpha PEP66? It is a rather large aluminum HS w/ Copper core. The fins are about 3" tall and has no mounting channel. It was designed around a ducting shroud that the fan attaches to and blows the air from side->side, not top->down.
http://www.overclockers.com/articles105/
Hope this helps.
Let me know if this is what you were looking for becuase I have one.