From a little research it appears that both front and rear suspensions from a Z31 may be able to be fitted to a 280ZX. The Z31 suspension seems to be an improvement eg less camber change at the rear, more caster at the front, but basically the same.

Has anyone tried this or done some research as to fitment and benefits? Opinions? Results?

 

I've done reasearch only on swapping the hubs and brakes. This gives a slight upgrade on braking components and a 5-lug pattern. I have not looked into the whole suspension swap but they are the same design. I doubt you get less camber because I see Z31's all the time with the rear cambered in like the 280ZX. They also have a lot of 'squat' just the the 280.
I'm hoping to do the 5-lug swap sometime. I was going to use the Z31 front struts but keep the stock 280ZX rear suspension and just swap on lugs.