Brown sugar: You can use light brown sugar, but the flavor won't be quite as strong.
Flour: I highly recommend weighing the flour (click "metric" just above the ingredients for the weights). If you don't have a kitchen scale, sift or stir the flour to break it up. Lightly spoon it into the measuring cup (don't scoop it) and then level.
Raisins: You can substitute other types of dried fruit, like dried cranberries, or chocolate chips.