How to insert block into Article content type?
Have you tried Insert Block?


  Sidebar blocks contain all sorts of nifty stuff, but sometimes you
  want to include or embed that stuff into the body of your node.
  Instead of using PHP snippets (a possible security hole on public
  sites), you can use this module. When it's activated...
  
  [block:name of module=delta of block]
  
  ...will insert the contents of a rendered sidebar block into the body
  of your node. If no delta is specified, the default block for that
  module will be displayed.


There's only dev releases for this module, but it has almost 6.000 installations.