FullsizeChevy.com - Chevy Trucks
Last I was there, the bulk of the site was devoted more to the more recent trucks (2000+), with a little bit of support for the older trucks, too (pre 1987). Seems that most of the original GMT400 trucks ('88-99) have either died and been buried, or have been sent to Mexico, in addition to all the replacement parts. That's why I finally got rid of my '89.
Replaced it with an '07 PSD.
-blaine