SB Head Casting Value

I am getting rid of a lot of my stuff. I have a set of serviceable 974 castings with the J on them.

They aren't worth much, but I don't want to give them away either. They look fine, no rust. Just came off an engine I got years ago. The block was a 71-74 360.

About what are really good cores of that casting worth?

Thank you, ROB