What's the best way to find a GM part number application?

[FWP]

I know about gmpartsdirect and acdelco. Are there any more good online sources for cross reference? I'm looking specifically for a good place to plug in a GM number, get a description and application.

 

[big83chevy4x4]

i use this
http://www.trademotion.com/partlocator/index.cfm?siteid=213800