The Plymouth and Dodge are two very different looking grilles in 1956, which do you have, and what are you trying to accomplish? Those are also two of the more popular grilles to swap into other cars, so I'm not sure why you'd want to change it. Ditch the bumper guards and the hood emblems, keep the grille bars stock. As mentioned, use a '55 center in a '56 Plymouth grille, if you have a '56 Dodge Custom Royal you can swap to a Coronet grille and it'll eliminate the teeth, bolt-on swap. Post a pic of your car maybe, easier to make suggestions.
Squablow......that is a car(s) that I have always like the way it looks, and will own one before I stop messin with cars. It just always seemed to be too much going on...kinda like the ' 57 Chevy. Not wanting to make drastic change, more like refining.