Hi Gilles
This used to be an easy part to find at NAPA but two years ago when I was doing the HUP kept coming in wrong, will look for the numbers we were using. In the end while looking in old boxes for a better number discovered I had a nearly new disk that I had set aside when I needed pressure plate as well.
If you are in a hurry give
http://www.obschevy.com/Pages/ShopOnline.html a call have your old disk in front of you when you call to confirm dimensions. They have disk and clutch pack listed.
Cheers Phil