The plates don’t have to be original to the car. You can buy a set of plates that would be correct for your year of car, bring them to the DMV to have them inspected and checked to make sure they’re clear. As long as they’re clear and in decent condition you should get approval to run them. You do need to have a pair and the condition is up to the person doing the inspection, so the required condition can be a moving target. The plates for the aforementioned ‘56 Austin Healey were added that way.
