The biggest Indian store in Dallas is called Taj Mahal 75 and Beltine. In a strip mall. They usually carry alot of stuff and there prices are generally less expensive thanth smaller stores.
The one in Irving that I go to is at 183 between Belt Line and Story Rd. If you take Belt Line North, and stay on the service road you can't miss it. They have a huge sign on the freeway that says Indian Supermarket.