Steve -
If you got two liters, you would be more than covered...that would even include the transmission. The final drive is a fill to the bottom of the threads. The driveshaft is 50-100cc...doesn't take much. The transmission is also bottom of the filler hole threads.
Vech at Benchmark Works can hook you up with a manual. There manuals on line...they were all the same for the /2 models, with entries for each model during the period. Duane Ausherman and Jeff Dean have manuals:
http://w6rec.com/duane/bmw/2man/index.htm
http://bmwdean.com/1966-owners-manual.htm