I have no idea at all, but thinking out loud...

Are the two MT boxes you refer to different (excluding the obvious 4x4 bit!)

Are the starter motor appertures on the same side of the 'bell housing' (even though MT75's don 't have a removable bell housing you know what I mean) you may need to swap the front cases over?

If you have to use the 4x4 Cos flywheel then you will have to use the 4x4 starter, clutch cable etc - well, I'd have thought so anyway?

The input shafts - are they different in any way? If they are then you may need to swap that over too?

You would probably need the propshaft from a 2.0 8v DOHC Sierra seeing as the basis of your gearbox is from a DOHC Sierra (okay, it might actually be from a Granada but the prop might be longer/shorter - I can't remember -also make sure the gearbox crossmember is form a Sierra - the garanada one does not fit.)

Like I said I have no idea and all what I have written might be total bollocks but you have to start imagining what might be different and checking it out for yourself. I'm sure I read of one white 3 door (adams105e - username?) where the geezer had done this but I might be wrong.

Good luck!