I've had a CA 1945/46 plate on my truck for many years and somewhere I have a DMV booklet that explains these two odd years re single plate. Of course in CA all this could have changed, bigger problem very few DMV workers know the rules re. YOM plates. I'll try to find my booklet and email you the pertinent pages.
In addition, there is a phone number you can call to speak to a person in the YOM dept, I used this number a couple years back so not sure if it still works.
YOM Field office support unit, 1 855 230 8747
Best of luck
Jim
