Hi Johnny,
I don't think you can really do that with these extensions as the requests to these types of files don't go through the DNN pipeline. See this for more details: http://www.ifinity.com.au/Blog/EntryId/90/Real-404-Error-Handling-in-DotNetNuke
Now you can potentially map out the .HTML extension to get processed by ASP.NET - http://www.ifinity.com.au/Blog/EntryId/66/How-To-301-Redirect-htm-or-html-pages-to-DotNetNuke-aspx-pages
Best regards,
Aderson