In Concrete5, how can I enable external links to 1) be indexed, and 2) show up in the search results, using the search block. I guess point 2 will automatically happen when 1 works?
Unfortunately there is no way to tap into the C5 search index in any way other than via blocks on a page or page properties (custom attributes). This means you cannot add external links to the search index in C5 because the pages that are linked to are not part of your site and hence have no concrete5 blocks on them, and also you can't set custom attributes on external links (although actually there is a roundabout way to do so, via the "Page Search" dashboard page -- but I have a feeling this is a bug in the system because setting those attributes doesn't actually do anything as far as I can tell).