This can only be done with application level redirection. In this kind of redirection the url with :8000 is sent to the browser, then depending on the type/version of the user agent (browser), it might or might not appear in the address bar (assuming there is an address bar in your user agent).
I once had a similar redirection for one of my forums using mod_rewrite and used Internet Explorer to visit the old addresses. Sometimes the new address would appear and sometimes the old one, and I'm not sure what decides that.
If it was a whole domain or subdomain with its own dedicated IP address, you can do that transparently by IP forwarding (network level redirection). But you want it for a single directory.