Quite a necro-posting, but...
I've missed killing the ghoul by the river in Act 1. In case I edit the save file to mark this quest finished, would the Huntsman still count it as a turned in item? I'm planning to do that right before talking to him the last time during Act 5.
UPD: I've collected my last monster part, edited the save file (unpacked, swapped quest script from a save that has the mob quest completed in Act 1, packed back up). The huntsman had no corresponding dialogue option even after I have turned the head in. So save editing doesn't really help you in case you have already missed an earlier quest.