Well I'm stumped. I had never noticed that the 1968 - BBB didn't address the 4.5 engine, and that it only addresses the 3.5 engine in terms of the coupes. I have another manual from Mercedes - Maintenance Manual Passenger Cars through 1977. It includes models 10, 108, 109, 111 coupes/convertibles, 107 roadster, 113, 114, 115, 116, 123 through 1977, looks like it starts around 1968. It's about 12" x 10" x 1", lots of info such as adjusting valves, tensioning belts, things that would be considered general maintenance. If you want it I'll shop CONUS $50. Pics attached.
I still think you are way better off with the BBB 1968 - for everything except engine stuff.