scotty b:

Re: Engine #
110.988-10- is correct for 1984 W123 280E/CE/TE. The -10 indicates the engine was originally equipped with a manual trans. Nominal rating of 185HP. 9.0:1 CR.

Re: Flywheels
On seeing the picture of the two flywheels, my thought was that the one on the engine was a remachined version of the separate one. However, since the engine was originally equipped for manual trans, I now think that the installed flywheel is the original M110 type, as Tom says.