340 Aluminum Edelbrock Heads & Intake Deep corroded Appearance

I bought this beautiful car in the late fall. But as you can see the aluminum heads and intake have a dirty brown look when I bought it. Not sure if it came from heat, oils etc. I would like to clean them without taking the engine out. Any suggestions? Any idea how this came to be?
thanks,
Ron
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To tell you the truth, I wouldn't mess with it myself. It's beautiful just the way it is. Well, maybe put the rest of the air cleaner on it. LOL