The labor by machine shops to rebuild those OE style heads will be one price. You can call them to get the price, then price the cost of aftermarket alum heads ready to run. As mentioned, some heads require different rockers, etc so be sure you are comparing apples to apples. To a lesser degree, the alum heads, alum intake, and even the alum water pump housing can go a long way to saving weight too. All of that depends on your budget as well as your intended use of the car. Nothing wrong with using all OE style parts for a daily driver either! For me, if I'm going to rebuild my engine, I want the best parts I can buy to make it live a long time, be dependable, and bring additional smiles to my face.