Thanks for the input. After I wrote my original, I contacted an engineering friend who corrected me: Aluminum is less noble than cast iron and the aluminum surfaces are in good shape. I'm scheduled to go over the pitting on the cast iron with the local Chrysler dealer, so I guess what I found is probably pretty normal.
Thanks again for your input.
Diardi 2004 Blaze Red Cpe. 13,540 otherwise happy miles.