I would also recommend the usage of the License Plate Changer by leftas - a configuration for maximum realism is listed in the readme. There are two ways you can install this: as a replacement, in which you replace the Yankton plates with these, or an addon.which I'm not so sure about, read the readme.
Sorry, I'll never say that again - this is my first license plate mod for GTA V! With thanks to WildBrick124 for giving me credit to use and giving help for modifying the plates in the first place, this is a modification of 'San Andreas (Yellow)' to fit with actual California license plates from 1956 to 1962. Ever wanted to go into the virtual wingadinga culture of the 50s? Ever wanted automatic, systematic, hydromatic, greasy (what?) static electricity? Have you ever craved the old California plates of the 1950s, but lore-friendly? Well, I have the plates for you, daddy-o.