I'd find the correct D44 and take a boatload of measurements (any SASed Xterras in your area?)... then you'll know what the differences are and you can make some judgments about whether a different axle is likely to work.

One of the reasons Calmini went with the one they did is because the 6 on 5.5" lug pattern matches Nissan's. If you don't mind running different wheels front and back (or if you're changing the rear too) then I'm sure there is a much broader range of axles that will work.