Water Pump Material Manufacture

[soduka]

I see water pumps advertised as made out of cast iron and water pumps made out of aluminum. Is there a reason to get one over the other?

 

[Pantera1973]

Aluminum is lighter, transfers heat better, doesn't rust, eliminates any problems of corrosion due to dissimilar metal contact, and is what the car came with from the factory.

Mark VIIIs have Aluminum Blocks & Heads so it makes sense to keep everything else in the cooling system Aluminum.