How many miles on yours? Have you done the rod bearings?

You can get 100 octane at a small number of gas stations in California, lots of them refer to it as “race gas”. Here’s a handy map someone else made of gas stations in CA that sell it: https://www.google.com/maps/d/viewer?mid=1yGUCmpCLUUPb4L_puE7bHQqXMlc