Thanks for the tip Carl, I'll give that a shot and see if it helps. After polishing, the aluminum does develop a dark/dull color after only a day or so.
I'm installing a 2nd gen water pump housing this weekend. I was amazed at the weight difference! That 1st gen housing weighs a ton! I also got a new 1st gen water pump, which looks like it will fit on the new housing, and it is also aluminum (which is cool, and a lot lighter than the original).