What is the best way to clean aluminum heads?

 

Are they still on the engine or are you rebuilding them?

 

Take them to a machine shop.

 

Lots of carb cleaner about 5 cans a tooth brush and a green scuff pad for the headmounting surface. Or if you feel like spending big bucks take it to a machine shop. Resurfacing heads isn't always necessary sometimes they take too much material off and you play hell trying to get your vehicle running right again. If you check the surface of the heads with a flat ruler make sure it's not warped you can get away with cleaning it and using a scotch pad on it.

 

If they are ff the truck, just have them acid dipped.
They will be as clean as they were from the factory.