1: the V8 pathy shafts should be the same for both sides.
2: the Titan rear axle is SOA, not an easy bolt in swap. You'd be looking at about 7" of lift in the rear, and into custom driveshafts, extended brake lines, etc. or cutting and welding spring perches.
3: if you want to run that combo, you'd be stock xterra width in front and 6" wider in the rear. That makes no sense. Posted via Mobile Device
Left and right shafts are the same. No difference.
Titan rear axle will NOT bolt into an Xterra. Wider, spring perches completely different, wheel bolt pattern different, driveshaft flange a different bolt pattern. But the finned diff cover off the Titan rear end will fit the M226 you have in your off-road edition (providing you don't have the oddball 2WD '05 off-road)