Site-Specific Headers/Footers

I'd like to have a mailing list that's archived with MHonArc 
available from two different web sites.  The twist is that I'd like 
each site's version to contain headers and footers (and corresponding 
web links) specifically for the host site, so that it completely 
integrates within that host site.  All index and message files would 
have host-specific headers and footers.

Is there anyway to just create the archive once, and then substitute 
site-specific headers and footers "on-the-fly"?

Any ideas and/or experiences would be greatly appreciated.

Jerry Werner