New here.. Nice place..
Welcome to FABO, Sunburnt, from SoCal. You're going to have fun here!
Great find. Hang on to that California 'black plate' (especially if you have the front plate also) and the license plate frame and display them with your car. If that may not be part of your plan, then you should know that you have a market here in California for the black plates from people with '65-vintage cars as California now allows registering your car with existing year-of-manufacture correct plates up to 1972 model years.
So, what's the plan for your '65? Restore or restomod?
Please post more pics, both current and as you progress with your build.