Well, make this sticky because it will save many people the $450 plus 2 hours of labor to attempt the install.
What I have on my wrx is:
JDM r180 rear diff
What I was using for a propeller shaft:
1995 Automatic Impreza shaft
What I tried to fit:
USDM Sti 2004 propeller shaft
The end result:
It is 1:30 am and I am furious The diff hub holes do not line up with the USDM end hub/flange. I've taken a few pictures to show the difference from the auto shaft holes to the USDM Sti one. The auto shaft did fit, I just wanted something beefier.
Close to lining up
Opps, not really
I recall a few people stating it would fit, I guess until you personally try do not rely on 2nd hand info I'm just pissed from spending 2 hours on my back for nothing.