280Z or 240Z suspension?

[Homepup]

I'm in a weird situation. I ordered new rear struts for my 1973 240Z (which has been all original on everything I've touched so far) but noticed they don't fit exactly (diameter of the strut housing is larger and the strut nut that came with the new strut is too small). After comparing to a spare rear suspension I picked up, the struts fit on that one fine.

I'm guessing that someone must have swapped in a 280Z rear suspension at some point (there's number on the outside, Nissan 55303 N4600 AMPCO Japan) and the spare one I have on hand is the actual one for a 240Z.

I'm now debating, do I return the struts I just ordered and pickup some new 280Z struts that will fit (since I've already rebuilt the brakes and seem fairly certain that the rear bearings are ok) or swap out this one for the spare 240Z rear suspension (but I'm not sure of the condition of the rest of the parts in it and I'd have to change both sides obviously but only have the drivers side removed currently)?

Are there any downsides to leaving it as a 280Z rear suspension? I notice the strut housing is almost 2 inches higher along with being a larger diameter. I haven't looked to try and identify if the differential was also swapped but welcome hints on how to do so easily. Any issues if it was still a 240Z diff with the 280Z suspension? Would seem odd that someone might swap in a 280Z diff but leave it the original 4-speed transmission.

[rturbo 930]

As you mentioned, the rear strut housing is longer on a 280Z. I'm surprised the rear of the car isn't sitting higher than the front, which would be a dead giveaway that something isn't right. I would definitely swap the 240z rear struts in. The 280Z rear strut towers are something like 2.5-2.75" taller than 240Z strut towers, IIRC, and the top mount is about 1" taller on top of the strut tubes being longer. It seems strange to me that someone would completely swap the rear struts for no reason, so I think I'd look over the ones you have before committing to using them. If they're no good, I'd probably sell the 280Z struts for a correct set of good 240Z struts. 

 

The diff is up to you. People swap R200 (280Z) differentials into 240Zs, and R180 (240Z) diffs into 280Zs. It's separate from the suspension. If you don't need the strength of the R200, but want a limited slip, a Subaru R180 is a good way to get a limited slip into the car. 

[Homepup]

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.