Well now. I've just about reached a conclusion, dependent on two assumptions about the preamble. The first is that the two head start clues don't have an answer to be replaced. They just don't have an answer. The second is that the substituted letters bit only makes sense if I use the letters of the successful hunter, because they account for the letters of the two items negotiated by the more modern hunter (with one letter adrift, I think).
What I can't resolve is which final letters to highlight: as others have mentioned, there doesn't seem to be anything unique about three of the (presumed) letters: I must be still missing something.