for that money just get a v8 4x4 truck ;-)IMO, it would be easier to swap an H6 into a 5MT 2.5. The clutch and everything would be there and all you'd need to do is swap the ECU.
I woud love to throw an H6 into a Baja with a lift and some 33" tires... yee haw!
But honestly, for the money invested, just buy a 2.5XT and mod the up/downpipe and give it a tune.
and yeah, you CAN do anything...
http://legacygt.com/forums/showthread.php/my-subaru-beat-buick-heart-140053.html