XF 1.4 Trying to add a header for posts

Hi all. I'm trying to add a header above posts like this. I've tried it by placing the code in the message template right under the opening <li id="{messageId}"...>. I can position it where I want it to however I only want it to appear on top of posts and not conversations. Is there some sort of conditional I can use? Or another template I am missing that might be a better placement?