[ShaneHobson]

I learnt the hard way that you can't run a 4.44 transmission with a 3.9 rear diff. (We swapped the trans without knowing it was 4.44).

AFAIK, you can physically bolt in the 4.44 rear diff without modifying anything (ie no cutting etc), but you will wind up the centre diff causing shuddering and other nasty drive train stresses until something goes boom or you replace the standard transmission with a Legacy transmission.

The Legacy transmission swap seems to be straight forward, again we just unbolted the blown SVX trans and bolted up a Legacy trans without any hassle.

You should wait for someone more knowledgable than me to chime in before proceeding to pull your car apart though.