All looks normal to me, connected to the factory brackets on the diff. And yes it's a std Nissan arm.
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Just had another look at the pic on the computer rather than the iPhone. when i first looked at it it looked like that was a plate down the inside of the radius arm and i thought that might have been one of those SuperFlex arms but the rest of the arm looked stock. Was strange and i could not see past that image.
You are right though, it is the mounting bracket welded to the diff that i am looking at and as such all looks stock.
To the OP, check to make sure that you have rubber bushes in those radius arms, if they are rubber then there will likely be no caster correction built into them and your then running Drop Boxes and it should be sweet.