Thanks for the reply. Yeah, I'm clueless as to why it would have been swapped in the first place. This is the very first piece of the car I believe to not be original, and I have been through EVERYTHING on this car.
I obtained the spare rear suspension that I believe is from a 240Z from a separate person than who I bought the car from, so I don't believe it was the original one that came with it.
I agree, I think I'm going to swap it in since I've noticed there's a dent/bend in one of the suspension bars on the 280 suspension I took off. Of course this means I'll have to swap out the other side too (no biggie since I was eventually going to pull it out to put in the new strut) and will move over all the rebuilt brake parts that I completely replaced last year. From what I can tell, the bearings seem ok in the 240 rear wheels too so that's good.