Old cast iron motosr and how to tell cast iron from steel ?

I'm new to the forum so bear with me.
I had a couple of engine blocks I tore down pulled the crankshafts out and rods and pistons because they are still usable.
Question I have is what do you do with the cylinder heads ?
Do you remove the valves and springs so you can get clean cast iron prices for the srap?
I have a cast iron pile I am putting together old rotors, engine blocks, and would like to get the clean cast iron price when I go to the scrap yard.
Another question, is there a way to tell cast iron from forged steel ?
I did try sparking and viewing the color of the sparks, but the sparks were orange in color on the steel and also the cast iron. Could not tell a difference, is there another way to distinguish between the two?
I'm hearing steel is 200.00 per ton.
And Cast Iron is 300.00 per ton.
Thanks in advance for your replies.