CA will issue 1960's era license plates made from original molds found at Folsom State Prision. http://www.latimes.com/business/autos/la-fi-hy-california-black-license-plates-20150622-story.html
Odd story to come out now as this is pretty old news. My wife and I both ordered these plates last year for our 2008 and 2009 retro styled Mustangs and they arrived last fall. We must say they look great on our cars but agree they look a bit odd on modern cars. Not sure what other's plates were made out of but ours are aluminum.
I'll be getting a set for my '71 GMC even though a blue/gold version would be correct because I like them much better than the current issue plates on there now plus they'll look fine as there was no real change in GMC styling from '67-'72 anyway.
Yom plates are another way to go ,a little more hassle but unless the rate has changed they are a extra 30 a year but can only be used on the year of the car they where originally on .Plates are at the swap meets and all over the price range.
21.175 Year of Manufacture (YOM) License Plates (CVC §5004.1)
Year of Manufacture (YOM) license plates are any officially manufactured California license plates issued in:
1969 or prior, for autos, trailers, and motorcycles, and
1972 or prior, for commercial vehicles.
In lieu of the license plates otherwise required for the vehicle, YOM plates may be assigned to any currently registered:
1969 or older year model auto, motorcycle, or trailer of a corresponding model year, or
1972 or older commercial vehicle of a corresponding model year.