Hard to say without the details but I'd say anywhere from worthless junk to $2500 depending upon condition, porting, and valve train components. I'd say $1000-$1500 for a pair with unknown valve train and porting but otherwise good condition. To me good condition means they haven't been excessively decked, the combustion chambers aren't altered or been blown up, and the ports aren't all hogged out. On the flip side, if they have been nicely worked, with good valve train and flow data, that could push them to the upper end of the range. Virgin heads are also in the category.
Intakes in decent shape $400-$750.
I have a number of C302B and BF301 heads. They are great performers and in the hands of the right person every bit as good as about anything available today, at least for street car enthusiast. Good for Panteras but you can't run them on shock tower cars because the exhaust ports exit too high.