I am looking at putting a viper system in my blazer. And I need to know what bypass I need for the anti theft system and also if I need any kind of module for the locks? Also if anyone knows the polarity of the locks it would be greatly appreciated.

 

This will help on the wiring side of things:
2000 Chevrolet Blazer S-Series Alarm Information

You need a passlock bypass module. Most resellers will match their product to your application. I have used the Fortin INT-SL in the past and it worked very well. I used it in my old '04 Rainier and it handled everything. For the s-series trucks, there is a lot more wiring that needs to be tapped into since the door locks, etc are not controlled through the serial bus network.