I can tell you this, about twenty years ago, I pulled the A250 out of my Dad's 75 D100 and swapped in the A833 OD trans w/ cast iron case that they had put in the trucks. Bell housing remained the same. Beyond that, from what I've read and seen done, its strictly an issue of the input shaft support being the correct diameter to fit the bellhousing. Having said that, things may be different than I've seen.