http://1500bc.com/pretf/diaclone_pictures.htmlHere's one place that popped up in a internet search.
Fortress X was one of 2 big robot bases, GRB - Great Robot Base and Fort X.
Both I believe were designed by the future Transformers Base creators and you can see recycled aspects from Pre-TF bases in the TF ones (including Scorp)
X has a unique elevator system built in. Which almost makes up for his lack of transformability...it just doesn't turn into anything really, unless you really use your imagination, lay it flat and pretend its a star ship or something.
These "Stasis Pods" I was talking about are little yellow coffin like boxes, which drivers fit inside. IF you take the pod and put it in the back of one of the tanks, and back it in, with the cleaver use of the elevator leavers you can hoist the pod up inside, higher and higher till it reaches the bridge, then move it down another chute into the other tank, or into either of the arm ships. The whole thing has slides and such built in, with magnetic platforms all over.
Another cool thing is his head, the side wings can fold in to make a face plate. I'm pretty sure its got a solid Die cast part. GRB is all plastic. X is taller than Metroplex, but not by much. I think his shape resembles Scorp, but he has more features of Max, especially the foot docks. (GRB and X have spring loaded foot docks...grrr TF cut backs)
Like many of the early TF ancestors he came with lots of accessories, focused around the drivers. 2 Foot tanks, 2 different arm ships that rocket punch off. 3 stasis pods. And 5 drivers (solid colored head phone class).
GRB came with 2 rocket cars, hidden in his feet, the head jet (wish I had that), 2 big rocket punch fists with holes in the wrist which a driver could sit in (why?) and the replacement cannon for his arm. Also had the rubber ramp with the magnetic bits so you could escalator your drivers in the back door. Oh and 4 or 5 weird rockets that clamped to his hips and launched from a platform inside.
If you can find one, and it’s a good deal GO for it! Once in a great while (maybe once a year or so) parts turn up...so don't hold your breath.