I went to the California DMV website, and it looks like you can NOT register a Year Of Manufacture (YOM) license plate in California. So I agree with Erik - your plate would make the package more attractive. But it won't add a huge amount of value.
Maryland (where I used to live) and Virginia (where I live now) DO issue "Historic" tags, and DO allow you to register YOM tags.
This got me going on a new project - a
list of all the states and whether they issue "Historic" tags, and whether they allow you to register YOM tags.
Take a look at what Nevada does for YOM plates.
-----
Folks - It's gonna take me a long time to go through all the states.
YOU CAN HELP.
What does your state allow?