Some more pics here for your amusement
http://www.pc-look.com/boutik/Plus_128003-015.php
have a pike at the top one, Brian
The fins would probably do most of the work. If you look at the surface area, in this case the base of each rad = 0.1m² and the fins approx 0.25m²
Total area roughly 0.7m²
Considering H = 5-10w/m²K
then you have an air side C/W of 0.14-0.29 °C/W
No idea what the liquid side C/W would behave like. For the rad I would think it may even be negligeable!?