[NOTE:] This was originally published on my Shapeways store, tested using their printers. Tolerances may need to be adjusted.
This is a head, a transforming neck joint, and a back spike kit for Titans Return Voyager Galvatron to remove the Titanmaster head, its port, the flip-up helmet, and the back kibble for the jet mode. There is an arm cannon adapter in the photos but it wasn't my model and is not included.
Installation for the neck involves removing screws from the pelvis and torso for disassembly and replacing the grey piece the stock head plugged into. The back spike is also easy to install as the pin on the figure's back kibble is easy to push out with anything thin and sturdy enough. The cannon mode transformation is completely unaffected as you can see in the photos.