I have been following this discussion out of curiosity about this problem. I haven't seen the flywheel mentioned, and you guys seem to have tried most other things. Is it possible that the flywheel is not true to the crankshaft or the surface is machined at an angle other than 90 degrees to the crank? Is the drive shaft yoke on the front of the rear end true? I don't mean to but in but these things might bear a look. I'll keep watching to see what you find.
best wishes, Les
