(Ken) You would have to order a custom plate to be spaced accordingly. Thus the reason you got 6 digits sequential.
Although you could custom order plates with a space in there, you can not order with 3 letters, a space, and then 3 numbers like original - but could come close to that and look somewhat right.
Best to just get a nice set of original black plates and put them on your 63-69 car. These new plates are pretty ridiculous and honestly no need with so many used and available sets out there.
The YOM route in my opinion is easy too if you really want black plates:
https://www.dmv.ca.gov/portal/dmv/?1...k/ch21/ch21_36