Changing block templates based on context? moving title in body field in template Is it possible to change my block template suggestion based on a particular context?

E.g. On certain parent landing pages (I could manually set; because there are only 3 conditions no determinate pattern), I need the block title to go inside the content &lt;div&gt;. 

I could do a workaround and add the title in the body field. Although, I don't want to modify the block content (to add title in the body area/field) because they maybe used on other taxonomy pages; and the clients will have a hard time managing this (calls asking why is the title shown twice in the block management).

Would or could this be best in terms of most efficient solution achieved by preprocessing?

Current output on pages (Default drupal templates in psuedocode):

div.block-block-{delta}
  h2.block-title
  div.content


Desired output (on set parent landing pages)

   div.block-block-{delta}
     div.content
       h2.block-title


Desired output (on all other taxonomy pages)

div.block-block-{delta}
  h2.block-title
  div.content


Update:

These landing pages are just three nodes that the client wants. Theres not really a rhyme or reason to what determines if it is a landing page. I just need to set three node id's to trigger the block template change.
You mention the word 'context' in the first line of your question. Take a look at the Context module. I just came from this page 

http://www.metachunk.com/blog/context-based-template-suggestions-drupal-7

Edit: elaborating .. here's the context module 
http://drupal.org/project/context
Install it and create a context 'mycontext' for your 3 pages.

Based on this context, provide a template suggestion as mentioned in Topsitemakers' answer. In your themes template.php, it should be something like (not tested)

mytheme_preprocess_block($&amp;vars) {
  $context = context_get();
  if(isset($context['context']['mycontext'])) {
    $vars['theme_hook_suggestions'][] = "block__mycontext";
  }
}


You can do this more generic as described in the post linked above. Now, your block will render using block--mycontext.tpl.php, if it exists, when shown in the 'mycontext' context. 

$2c,
*-pike