The salvage yards in San Diego were all by Brown Field near the border. The city has been buying out the yards to make room for development and Its gotten to the point where there is only a small handful on Energy Way in Chula Vista.
With that being said there is a yard that specializes in GM up in East LA's San Gabriel Valley. They advertise primarily on Craigslist.
https://losangeles.craigslist.org/se...ch=2~gallery~0