Vintage Illinois plates 50's, 60's and 70's

I'm in Illinois and do this on my 78 fury, just keep my "a/v" plates in the back seat am I supposed to go tell the DMV that I'm running same year plates as my car? I found the ones I have on my car "by chance" when I helped clean out my deceased neighbor 's garage. No, I didn't buy my car from him...