There are a number of 1960s price lists "floating around" with members of the Vintage Airstream Club. I have 1964
but nothing more recent. You might try posting your question to the VAC discussion list to see if one of the 1967
Owners might have the price list with the information that you need. My guess based on 1964
prices would be something slightly in excess of $7,000 for the Ambassador by 1967
Vintage Airstream Club Discussion List
There is a thread about the 2004 models and pricing here on the Forums. I suspect that a 28' Safari would probably be a good comparison for a regular Land Yacht while the Classic line might be better for an International Series coach.
Good luck in your quest to gather information for your insurance carrier!