Lawton at Top Flight Corvette in San Diego did a lot of work on my ZR-1 for the previous owner but that was at least 15-20 years ago, the work seemed fine to me. I have heard good things about Power House Racing, I think he worked previous at American Heritage Performance in CA that has a great reputation for C6/C7. How about Bill B?
http://www.zfdoc.com/
I understand he is not in CA but probably the expert out west or Corey
https://www.hendersonperformance.com/