If you are in the USA I cannot imagine why you need worry about one cubic centimeter on the registration. automobiles such as Mercedes... 3.2 L (3,199 cc)... so, there registrations never say 3,199cc they fudge the extra cc.
I bought my 2011 diamo torino from someone who inherited it from their grandfather who lived in another state. It runs great... until... it is overheating. The waterpump spins... they look well engineered. I have diagonosed the problem as a stuck therommostat. I am getting ready to simply take it out (I live on the NC coast) and see if that gets the coolant pumping again. Meanwhile, I am looking for a place that sells parts. Have you found one?