65 Dart Mirror

many times the mirror mounting surface is not backed with a nut plate that would sandwich the door skin between the nut plate and the mirror base. In such application distortion of the skin metal is common and will cause a rise due to the incline plane of the screw when torque is applied. The question here on if/should is are you going back with the same mirror and screw and did the mirror hold tight before removed. I would probably just back the hole and level with a light tap if utilizing same mirror and attachment means. If I have suspect of weak metal and know the screw may not hold, I most always use a nutsert in the hole and swap to a stainless machine screw. What level method you chose will work just what are you comfortable with is the call you have to make.