I found a couple of original ''30 California plates...
DMV looked them up in a big-ol book to get dimensions and colors - verified they were correct. Then the photocopied them, filled out a form, and entered a bunch of stuff into the computer. They Faxed the whole package to the capitol for approval. Told me I would get a new title in the mail with either the new(old) number which would indicate approval, or with the original number and a reason.
What surprised me was the effort they put into it. It was an out-of-the-ordinary request for them and instead of being annoyed, they actually put a lot of effort into getting it through the system.
The plates are nice enough that I'm not going to do anything but bolt them on.
If they get denyed I have a "plan B". I'll get vanity plates with the same number (which can be done on-line) and when they come, the new ones will go in the closet.