Probably the best way is to implement a 404 handler of some kind. It should see if there are lowercase letters in the url and then redirect to the uppercase version.
If you need help implementing a 404 handler, try looking at a simple plugin that handles 404s, such as this one: http://crowdfavorite.com/wordpress/plugins/404-notifier/
I’m not sure why you would want to pass instead of redirecting. If you redirect with a 301 status code, Google should update their index.