Any1 know some good sites that have a lot of performance and stock parts for the 400 block??

Most of the Pontiac-specific sites aren't geared towards sales. They're all about information.

krepowre.com (Kaufmann Racing Engines)
jimbutlerperformance.com
centralvirginiamachine.com
indianadventures.com

These are commercial sites with offerings specifically for Pontiacs. You will find, if you're building a relatively stock engine, you don't need Pontiac-specific sites, just a good parts man. All the regular rebuild and mild high performance stuff from the factory is still available through traditional parts outlets. You just need to know WHAT you're looking for. Did you order Jim's book yet?