I had a couple or three of the 108 systems in use when I worked at KQKQ/KKAR in Omaha, Nebraska several years ago. I retired them when we bought Gentner systems and put the 108s in storage.
The stations have changed ownership and location since then, so I have no idea if they still have the hardware or manuals on hand. But it couldn't hurt to drop a line to the current engineering staff.