I've bought several parts trucks hoping to score some good doors. Today I think I have eight rear doors (four sets) and only one set that is any good.
Good ones are not easy to find. If you can't find a good set of doors for sale, follow every ad you find for a panel or Suburban and you may find some along with more parts. The alternative is to repair some that may seem beyond hope.
My best set came off a $100 parts truck and spent time in a body shop before being really good.