I will just ask this, but isn't the MS6 trans just a ratio modified ST220 Durashift with the AWD transfer housing?
If so, I looked into an ST220 sixspeed when I had my transmission upgraded (not the one that died) last fall. The durashift is longer and will not fit without subframe modifications.
Between this and the prohibitive costs involved, I abandoned the project, in favor of a building up a better mtx-75.
Great work on the M6 trans though, love to see this kinda stuff. Now how about shedding 410lbs and cramming that v8 into a tour?