You've got a good start to resolve the problem. Did your 201 chassis have a 4 or 6cyl. engine in it? When I first did mine I didn't want to cut the radiator header out of the car and this caused me to install the motor/tranny vertically into the car while it was raised off the floor. Later on I cut the support and made it removeable or you can adapt the 6cyl. one in. This saves lots of effort/grief down the road later on.
Use a dial indicator to double check for any runout between the engine and tranny as this will cause problems quickly if not running true. Can you also use the M5 pilot bearing in the end of the crankshaft or have to use a custom made bronze one? When making the flywheel, don't bother with an aluminum one as they are for racing etc and the engine will idle better with more mass...just like OE! A good steel one, not cast iron, will work just fine.
Keep us posted as to your advancement on your project....

TobiasMB
190/5.8