I just picked up a pair of heads I'm trying to find out if they are factory originals. The castings are D0A 4v closed chamber. They have adjustable valve train and C9 factory guide plates. None of my books show a D0A head let alone any 1970 head with adjustable valve train (beside boss 302). I would have just thought these were converted, but the whole thing sure looks factory. Any help from a true cleveland junkie would be great. I would hate to screw around with these and find out that they are someting special.