I have came across some buick heads #25518445.
A machine shop went out of business and a individual bought up all there engine components from the shop. He is selling all the engine stuff that isn't chevy. These heads appear to have already been re-worked and he doesn't know they are buick heads. What would be a fair price to offer him?
Hard to say without seeing the port work. Typically you can get the heads from the "U Pull It" type places for $50-100 (a pair). If the heads haven't been decked too much or radically altered, they might be worth $150-200, IMHO.