V.3 version of N20 Motor Bracket 2 is used when the N20 Motor Bracket is mounted in front of the metal brackets and the bolts need to be sunken in to have a flat front surface.
V.1 version of N20 Motor Bracket 2 is used when the N20 Motor Bracket is mounted behind the metal brackets.
Watch tutorial of how to mount DC Motor bracket – 2 on Totem Mechanics (video from 49 sec.):