What you can do if you really want to keep the customized look and feel is
to take all of the HTML modifications and drop them into a page and then
wrap it with the container placeholders that WSS v3 uses to fill the content
of the page. Build it out the way that you like, or so it looks similar or
the same depending on how much time you want to spend looking like the
original.

In terms of keeping a FrontPage unghosted  look and feel, best of luck as
it's not supported.