The transoms were switched to all composite about mid way through model year 1988… If it an ’88 get the serial number and call Ranger they will tell you for certain. If it’s 1989 or newer the transom is wood free. The floors of all 680’s were wood, but I have never heard of any of the 680’s needing a floor replacement. Not that they can’t but seemingly quite rare.
The 680’s were made until the early nineties with a few upgrades like making an integrated gas tank in the bow. Then it became a 681 and was made until 1999.