ca. black plates

hi folks i'm looking for some input on using the ca. black plates that were used between 1963-1969. i would like to buy a set for my 68 barracuda.there are a few on e-bay that say dmv clear but will i be charged more money when i go to the dmv with the plates i buy and renew the registraion? the white plates i have on it now are just plain ugly
thanks
terry