69 Dart Glove Box Trim

Ok, up front, this is a potentially stupid question. I searched for this through the site, but couldn't find the answer if it was there.

I have a '69 Dart that has the two piece dash trim (gauges and heater/radio). I have bought the pieces to convert it to the three piece (replacing the center and adding the glove box). I figure I'm going to have to drill, but as I dry fit it seems like I need to drill larger holes on the exterior than the interior. Is that the case or was there a different glove box door for the cars that had the trim piece?

Also, if anyone else has done this, did you happen to write down the measurements? I get nervous with a drill on good sheet metal...newbie thing I guess.