Thanks for all your replies so far on this topic!
Progress has been great:
The engine bay has been cleaned and freshened up and the 280 se engine was partly stripped to replace a couple of gaskets just to be sure I will be driving for the years to come instead of having a failure anywere soon.
cilinders and head look very good for what I have seen untill now.
The only thing I found strange is that the head gasket that came out was different to what I was expecting:
The m130 engine number is:980 10 0279 xxxx . I cannot find the source again but recall that this engine number would mean a late oval type gasket. (Wrote down 980 10 017 and higher : oval in my notes)
The head however turns out to be having the square shape . Which corresponds with my head number (130 016 0001 and the information on this great link:
https://www.sl113.org/wiki/Engine/CylinderHeadDid my first assumption about the engine number go wrong? Or do I have an later block with an earlier head?
Second ; i opened the flywheel that i had in storage and found a 127 number on it and only 1 balance lump on it.
I suppose I will have to go and look for a m130 flywheel for a manual w108 or so: are all these m130 flywheels out there compatible with the gearbox bellhousing and intermediate plate for my sedan manual gearbox? And can i use any pressure group on that? Or do i have to be aware of different pressure groups and throwout bearings (i prefer to find a diafragm group for a 280)
And will the gearbox shaft fit in the standard w108 pilot bearing that i will order to be placed in the crankshaft end?
Thanks for helping out!