Mount the gauge mount over the factory pillar.  Hold it up tight against the headliner.  Press the door molding back into place and make a light pencil mark along the molding for a reference for the 2 fasteners.  In some applications you will be able to install the fasteners underneath the molding, concealing them.  This was not the case in this installation.  There wasn't enough material on the factory pillar.  Find a suitable location for the 2 fasteners. While holding the gauge mount up tight against the headliner, drill 2 holes with a 3/16" drill bit for the fasteners.   You will be drilling the other 2 fastener holes (windshield side) later.
SPECIAL NOTE: When you finally install the gauge mount, check your location of the 2 fasteners that will be on the windshield side of the mount.  If the holes you drilled are on top of the factory metal chassis that runs the length of the A-pillar, you may need to trim the length of the fasteners to prevent them from coming in contact with the metal below them. If they do hit the chassis, they will not be able to be inserted all the way, causing the paint on them to come off.