The problem is when the old snaps are removed. Drilling out usually spins the snap stud in the hole and makes the hole bigger. There are a couple ways to do it... use a small washer and a small trim screw. Put the snap side on a piece of wood and tap the screw into the snap stud.
Originally, they would have been installed with a rivet squeezer with a special tip to get the rolled edge. NPD sells a tool that does the same thing on the 65/66 vent frame gaskets. Otherwise, you can buy the $200 aviation grade hand rivet squeezer, which would do the job.