Forget the first 2 pages of this section as they are for a 617.
the rest concerns timing of the IP you have.
Please note that the IP timing when using something that is going into that plug hole on the side of the Fuel Injection Pump Governor is 14 degrees to + O.5 degrees ATDC (After Top Dead Center); it is on the last page of this secition. (after 1990)
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Maintenance/My81/0760.pdf
There is a Locking/Timing pin that you can buy that also goes in that hole but to use it you would be required to pull the pump out. Follow the directions on inserting the Locking Pin and re-insert the Fuel Injection Pump with the piston on the compression stroke and the Crankshaft Damper degrees ant 14 Degrees ATDC.
I do not think you can just Eyeball through the plug hole and get the timing corect.
The site below if for the whole Engine; should be able to find all the info you want there.
http://www.ps2cho.net/downloads/MB%20CD/W124/Index/602_603index.html