I am wondering what the simularities and/or differences would be from the Sea of Dust in Greyhawk and the Anauroch in Forgotten Realms???I am thinking of linking these two places by a portal in my game

WHat differences do you mean. Of course the people and animals that live there are a bit different but you can make up almost everything as DM.So the players may recognize that not everything is the same in Forgotten Realms but you can choose by yourself what you want to have to be different.