There's quite a bit of discussion about it on hybridz.org. Essentially, you need the 27 spline custom output flanges sold by Wolf Creek Racing in the US, which will allow you to bolt up the Z half shafts. That is the only plug and play solution. $500 for the pair. Then you need to swap the input flange from the Z diff to the Subaru one. After that, it's a straight bolt in.
I've been giving this one serious thought too as opposed to swapping to an R200. Less clearance issues with my exhaust in keeping an R180, and an easy way to go LSD. Main issue seems to be finding a reasonably priced 3.9 subaru R180. The couple on eBay are twice the price of the 4.444 versions. I've only been browsing though so should maybe speak to some of the various Subaru breakers.