I have heard this go both ways...
Some get away with one plate, some offices make you bring 2. The time I was there, they actually photocopied the plates to send the to Sacramento.
A lot of the guys that peddle the original stickers say that the DMV looks a the numbers on the sticker, but that's just BS.
The '56 plates were actually issued in aluminum for awhile during 1960. I have a pair, and the paint is really shiny in comparison, and they dent very easily.
I know the repop plates you're talking about...and I will use them on my next go around after I have the legit plates approved at DMV. I wouldn't bring a real one and a reproduction in together though, as they look different when side by side. The characters are very similar but the "56" stamping is a little different.
Todd
Todd in Central California...about half way between Fresno and Sacramento
1956 Thunderbird - 1960 F-100 - 1961 Starliner - 1961 Imperial