I lived in Alaska for eleven years. I have made two round trips from Maine to Alaska towing a fifth wheel ( I now have a Class C)
You would be foolish to take a RV to Alaska: through Canada and up the Alcan without a spare tire and other emergency equipment. Even thought the Alcan highway is much improved there are places where you are hours (not minutes) from help and areas where there is no cell phone service. In many areas of Alaska the roads are unpaved and in rough shape. RVing to Alaska is not a Sunday jaunt, it is an adventure. And remember that if something can go wrong, it probably will. A spare tire is a small expense compared to a ruined vacation caused by a blow out or flat in a remote area.