I dont know, I would think that they would go for a quite bit more than a few hundered bones. Do a search on ebay and see what has sold. That should give a good feeling for the market.
One use for them was as Ram Air 3 heads. They are also the standard head for a manual transmission 400 for the 1970 GTO or Firebird. In good condition they would be worth about $400 - and up to $500 for the correct date codes for someone wanting to do a restoration (as pointed out above).