Audio Systems: Stereo Upgrades, customer serice, best bet

Question
How can I find out what newer model stereo components will work in my vehicle.  Example, I found a am/fm/radio/cd/cass from a 2004 Blazer...although it physically looks like it will fit, I am sure GM had better things to do than make it easy for us.  Is there a website or book where this kind of info is avaialble ?

Answer
Joe,

 your best bet is to call GM they have a customer serice line in the back of your owners manual ... tell them what you have and what you are trying to fit into it and they should be able to give you the run down ... hope this helps you out if you need anything else let me know !

thanks

CM