They use acid in the process and it also surface hardens the aluminum, its not adding anything so it should not affect its cooling. Sounds like a good test, atleast the Ebay FMICs are cheap compared to a sparco bar/plate core with custom endtanks, if it does not work that is.
Edit: The anodizing process does add a little thickness, read here:
http://en.wikipedia.org/wiki/Anodising
It sounds like it depends on how think they make it.
~John
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