If you don't have a factory repair manual get one. They are VERY useful when doing something you don't do every day. I got them for my Rambler and am damn glad I did. The drums look like they may need to be turned. But often they have been turned out too the limit over the years. There is usually a little lip at the edge of the machined surface that is the limit. If yours has no little lip. You can see this right below the pencil tip, see on the inside where the shoes hit?
They can be measured as well of course but that little lip is usually a give away to how much more they can go. And if you have a REAL parts store in town (not the McParts stores like Auto Zone and the like) there is a good chance they have those shoes in stock. My local REAL parts store does.
Brian