This forum is fine for the purposes of your post. You are making an inquiry about an attachment; not building one.
The 190 that tractorchick is perched on belongs to Steve Guider, who is also a member of this forum. A totally separate company from Case, converted 190 models to the forklift you see and they also made a chain-trencher attachment. Steve's 190 is the only known surviving unit to date. Little is known about them, including the existence of drawings.