Too bad. I can still do a engine/trans swap later, if I still need to. Be nice, if I can find a good head.
I did engine swap on my '66 200 same as yours, an M115 engine from '74 200 W115 car, it's a 2.0L euro spec. same power as M121 2.0L (95 hp, 115 ft-lb of torque, redline at 6000 rpm, 9:1 comp.,no emission stuff), I chose the M115 because parts availability is easy, Stromberg carbs are easy to fix(few moving parts compared to M121 twin SOLEX 36-40 PDSI), reliable and reasonable fuel mileage(about 6-7 km/liter for city; 10-11 km/liter on highways). In my country (Philippines), during early 70's, Universal Motors Corp. who assembled W115's were built from CKD (complete knock-down) units came with 4-speed manual gearbox and engines built in Germany shipped over here to install.
the mods were:
1.) Fabricating engine mount brackets since the engine mount arm is short compared to M121. This is critical part of the work because the engine- gearbox assembly must be in line with the drive shaft to extend the flex disc's life and propeller shaft bearings.
2.) I used the original M121 4-speed manual gearbox, it'll bolt right up but 1 bolt less, I did some of grinding in the bell housing and chamfering the flywheel at the lathe just enough to turn without interference.
3.) I used the air cleaner housing from W115, radiator from W124, radiator fan from 240D(W123) engine, expansion tank from W126 and aux fan from BMW E36 car (the only non-MB part).
4.) I swap the early intake with later ones off from '81 W123 200.before the swap, I have problems with dieseling and emissions, with later intakes, the engine shut-off valve is now located on the intake manifold, the cylindrical shape thing beside the carb (unlike in early ones located below the carburetor and a timer relay) and bypass air bleeder valve improves idling and part load drivability.
right now, my 200 needs a full body repair,paint and some TLC.
M115 with early type intake manifold
M115 with upgraded intake manifold from W123 200