351n 64cc Yates Racing Heads

I have a set of 351N 64cc Yates Racing Cylinder Heads that I am wanting to sell. Can someone tell me what these are worth?

To get a general idea, go here..
 
http://www.joeheckracing.com/store/show_by_tags/Ford+Racing+Cylinder+Heads?category=Parts
 
Find the closest matching item.  This should give you a general idea based on the shape/condition of your heads verses new units.