Hm... Mark,
The only real manuals you need to get
are the both BBB from the factory.
And...,
if you want, perhaps the Haynes manual.
There is no extra separate M127 manual for our engines around,
at least not specific to the M127II (230 SL engine).
All info necessary for that engine is in the BBB "Passenger Cars from 1959 - 1967.
Achim