Oh, you are talking about Quoc's Z. It's not a Z31 man, it is a late 70's Z. I thought that may have been what you were referring to, but I was stuck on the Z31 part :-\ Sorry.
Here is the actual address. He moved it earlier, it has info on the Speed Sensor as well:
http://gripjunkies.larrychendesign.com/rb/
Modified by l0nestar at 6:30 AM 2/15/2007