The part you linked above is what you need to attach the Rugged Mount to the Ram arm. The Rugged Mount has four holes so the two hole Ram parts won't work properly.
Click the image below to see the part on the GPSCity site.
Want to know more about the Garmin Montana? See the Wisdom and FAQ Thread.
Want to know more about the Garmin VIRB? See here
"The motorcycle, being poorly designed for both flight and marine operation, sustained significant external and internal damage," police noted.