In terms of it fitting into the carrier housing with enough clearance, I don't see why it shouldn't. Not sure if the stock ring and pinion would be a problem.
The issue might be the spline count. Someone correct me if I'm mistaken but I believe the spline count of the axle shafts in an Xterra's Dana 44 of 31. Heavy duty Dana 44 axles have 30 spline count shafts.
So I am wondering. If you can get a locker to fit in the housing of the rear, why cant some one get some new axles that match the spline. I dont know if I am watching to much Hot Rod TV, but they put new axles in all the time.