A couple good online sources for part numbers are Wallace Racing and Fred Teufert's Pontiac page.
http://www.wallaceracing.com
http://www.teufert.net
Also, if you subscribe to this forum you'll have access to the online part number database (look in the section called subscriber forums). It's very handy, you can enter a part number and it will tell you what years and models that part was used. You can also search by group number or year. It's pretty inexpensive and worth the price.