I only the run the black and silver plates on my older Morgans. They seem to fit better. Funny thing though, I went to the DMV to register my 38 DHC, UK Registration CUY 503, following completion of its restoration, hoping to get some 'Vanity' plate commemorating something, anything, as long as it could have the Number CUY 503.
As it turned out the the normal Florida license CUY 503 was not taken, and I could have it. Now I drive with only the old black and silver UK plates, but keep the Florida plate under the seat, just in case I am ever stopped. I doubt it will happen though.
Cheers,