I'm interested to know what the going price is for a A12 GX head?

I was able to find one that has been renewed (shaved, polished, reseated and maybe more).
It comes with a matched inlet manifold which i believe is off a later a14 oval port, as its made for a downdraft carby and is also equipped with water cooling.

Any ideas on what it might be worth would be much appreciated as i wanted to make an offer for it that seemed reasonable.

cheers in advance