I use the 8.7 head when I can with the matching cam and 220a/219 32 mm carb. I think this give 10-20 more horsepower.
That sounds about right depending whether you mean DIN or SAE. Did you retard the ignition curve for that modification?
But back to Stalin's car. I composed some images showing the different Mercedes-Benz engine types.
1) The original M180 engine from a W187. Notice the correct "reverse hump" oil pan needed to accommodate the steering levers.
2) The same engine with the same front mount but with modern "front pot" oil pan.
3) The same engine family but from 1976. Notice the modern mount in the middle.
4) Mercedes-Benz V8 (here M116, but M117 and M119 are pretty close).
5) And as a bonus a Chevy small block V8 mount spot. Not middle, not front.
-Harry