I just went through this last week on my car. There is a third component on the original setup to keep the switch from spinning: it is a square “washer” that fits into the dash’s backside recess. The washer’s center hole has a flat spot that matches the one on the switch’s threaded barrel. The backside nut adjusts the depth. The flat spot along with the square shape of the washer keeps the barrel from spinning.
The aftermarket dashboard did not have the depth to let me use all three components. With the washer alone the chrome bezel ends up flush with the front of the switch. On an original dashboard there is plenty of depth for all three components. The aftermarket dash forced me to make the decision of which part to leave out.