No you cannot replace the VX drive with a GTi drive, but as Wicked_Bass is saying, the GTi powertube does fit in a VX and it allows the VX to be used with the GTi bolt.
Without it, the GTi bolt does not fit in a VX because of the rounded off powertube.
The GTi bolt fits right in a V2 clone and a Droid without any modification because of the way the powertube is designed in them.
Macdev Clone VX Brown/white
Safer 73/45 with Ninja SLP.