Do NOT open up the bellhousing. Why ruin (permanently modify) an expensive part? Turn the bearing retainer down to fit the bellhousing. It's a 5 minute process including setting up the lathe. That's what I did for my 833 OD. The bolt pattern on the retainer is the same as the non-OD pattern. There will be no problem with the big retainer being cut down.

Here's the pic I uploaded with transmission measurements:


We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon