[TYPO3] is 404 handling like microsoft.com possible with typo3?

[Surer Dink]

All,
  I am trying to do something that I thought would be pretty simple -
when a NotFound page is accessed, I would like the URL bar of the
browser to remain on the URL that was accessed, the status returned to
be 404, and the contents of the page that are returned to be the typo3
Sitemap page I have (/site_map/) - as an added bonus, it would be nice
to say "Sorry, page you requested was not found" up on top, but not
needed.  This is exactly what www.microsoft.com and www.apple.com do
currently, so I'll take that as a sign of "it's not a dumb idea to do
this."
  So far, the closest I could figure out to get to the desired
behavior is to set $TYPO3_CONF_VARS['FE']['pageNotFound_handling'] to
the full sitemap url - returns 301 (or 302?) followed by 200, NOT 404
- the result is that the URL in the browser changes and the search
engines get the wrong response code.
  I've read a multitude of posts on this list, on various forums,
blogs, and others on 404 handling in typo3.  It seems everyone
continues to have problems with this, and no one has "the answer".  I
am writing here in case people DO have the answer, and it's just lost
in mailing list archives/google amongst the thousands of resopnses
that .. are wrong or not helpful.
  Thanks!