The Headmaster Jrs in-series seem to be a semi-current development. Couldn't Devil-Z have stolen the Godmaster Transtectors from a "current" time period, and transwarped back in time to hide them on earth? Maybe to get them to soak up as much earth chokon power as possible while Z found or cultivated receptive units to bond with them?
That would work, if Devil Zed himself wasn't also an already ancient dude.
Legends gave him a proper origin story (one which I really like since it totally jibes with the G1 cartoon's lore as originally presented, and definitely feels like something the writers of Masterforce could have written into the show way back in the 1980s) in that he was created from evil energy that had been built up inside the Matrix back when the Quintessons owned it during their original rule of Cybertron, with said energy being released from the Matrix and dumped out into space by the Cybertronians when they took possession of the Matrix during their revolt against the Quints. This discarded evil Matrix energy became Devil Zed.
The slave rebellion against the Quintessons occurred 11 million years in the past, so it was around that time that Devil Zed was born (or at least began his birthing process, we don't exactly know how long it took the released energy to coalesce into his being, but surely it didn't take a whole 11 million years to do so).
Although, here's a thought that crossed my mind. When Optimus and the rest of the Ark crew were taking their 4-million-year nap on Earth, perhaps the Transtector body was built during that time because it was merely
believed that Optimus Prime was dead. He and his crew all disappeared from Cybertron for a very long time, so he could have very well been thought dead back on Cybertron, and thus the new body might have been built in the G Nebula 89 with the hopes of trying to resurrect him somehow, with whoever was in charge of the body's construction unaware that Optimus was actually still alive out there there in the universe, just in a deep sleep on some backwater planet called Earth.
...
And after thinking of that, I decided to double-check what was specifically said in the
clip show itself, and now I realize that at no point is the idea of resurrecting a deceased Optimus with this body ever actually brought up:
Shuta: "Oh yeah by the way, why do Convoy and Ginrai look alike? Tell me about it! Tell me!"
Grand: "Okay, okay. A new Transtector for Convoy was among the Transtectors stolen by Devil Z. Ginrai 'God On'-ed it, and that's why they look alike."
Shuta: "A hero from Planet Master was supposed to combine with the trailer to become Super Convoy, right?"
Grand: "That's right. But because a human 'God On'-ed it, instead the Cybertrons gained ten times the power."
So the whole "resurrection" thing was just an assumption we fans have had for all this time. Go figure.
I guess the Transtector body was merely created to be an upgrade for Optimus, with its creator possibly hoping to re-establish contact between Cybertron and Master sooner than later, given the notion of "A hero from Planet Master" meant to be added to the equation as well, sounding more like the Western Powermaster version of the gimmick than the Japanese Godmaster version. It's just that Optimus happened to go missing well before the completion of the body's construction. Whoops.
Funnily enough, Takara did put out that Nucleon Quest Super Convoy toy that was marketed in Japan as a Powermaster rather than a Godmaster, and which did use the "Super Convoy" name, almost as though that toy was meant to be the long-awaited realization of what Grand and Shuta said was the original intent of Ginrai's Transtector.