The center diff bearings failed on my 03 Outback (manual) and did a lot of damage, both gears are chewed up badly and the driveshaft bushing is scored. I happen to have a 98 Legacy that I'm scrapping and I'm wondering if I could swap over the complete rear end of the transmission onto the 03? I have both transmissions apart and the components (coupler, bearings shafts gears) are quite a bit different, so much so that I would have to swap over the complete rear case and all parts within.

Am I dreaming or is this possible?     

I'm quite curious about this. Have you figured it out?

how about just use the older trans in it's entirety instead of swapping guts?

 

speed sensor differences i'm unsure of....

 

it'll bolt to the engine, axles will slide right on, and both should be 4.11 final drive.

there are some 3.9 final drives - even in that case you could just swap the rear diff to match.

 

rear driveshaft length i'm uncertain about but that's easily determined if you've got the parts there to measure/compare and not hards to work around anyway. 

Hybrid transmission is definitely possible, and has been done. We did that in my friend's rally car, as he has a phase 1 jdm 4.111 transmission in it, but we wanted to put the sweet Group N 10 NM center diff, which is phase 2. Got the whole housing, transfer gears, and diff, and swapped it all over. Doable in the car. Much easier than swapping the whole trans.