Dwain Dement, Vision Motorsports built one of my motors (3.2 race motor) and many others that I've raced some 20+ years. In Orange County, Laguna Hills, CA
Vision Motorsports
In the SF Valley up your way, there's TRE Motorsports.
I've never had a motor built there, but Dave Bouzaglou is deservedly very well respected.
TRE Motorsports