I pick up a wii a few weeks ago and have to say I've found I really only use it for the VC games. Playing Zelda and Mario64 etc with the classic controller is pretty pants so I looked into getting the N64 controller working on the Wii.
After a bit of research I found
www.raphnet.net a very cool site. He sells pre flashed chips for converting lots of diferent controllers to the Wii so I sent of some paypal moola an waited about a week. Pretty fast shipping.
The wiring was extremely easy and worked flawlessly first time.
Heres a pic of the box I made for it and a pic of how it attaches.
If your interested in using older hardware with the Wii I highly recommend these pcbs.
PS I also put one of the prototype PulseVU2 chips in the Wii too, but I didnt take any pics of that.