In a large mixing bowl, whisk together the pumpkin, milk, eggs, pumpkin pie spice, and salt. Pour the mixture into the prepared pie crust. Bake for 15 minutes, lower the temperature to 350°F, and bake for another 40-50 minutes or until the filling is set. If the pie starts to get too brown, lay a piece of foil over the top of the pie, making sure the foil does not touch the filling. Let cool, then refrigerate overnight or until serving time. Can be made a day ahead.