Hi, this is a great site for DIYers. We are buying a new clothes dryer, and while I am installing it, I want to upgrade the existing 220/240 volt 30 amp 3 plug wall receptacle to the newer 4 plug. I have a six foot piece of Romex 10/3 w/g that i will pull through a finished wall using the old 10/2 as a fish wire. The existing standard size rectangular receptacle box is metal and is flush mounted in the wall. Would it be appropriate to use the same box or should I add an extension on the front of the box because of the extra wire? It looks like space inside the box would be tight but doable without the extension but I want to do it the right way. I know how to safely do the connections, been replacing other wires for years but this box issue is new to me. Or would a wall mounted double box be better? Thanks in advance for your help.