Japan is always the best place to look first, to see whats available.
http://www.nagisa-auto.com/products/nissan/m35.html
Following that, I think you have to risk attempting to fit parts from Y34/F50 for the rear upper arms and the rear spring bucket lowering perch http://www.nagisa-auto.com/products/nissan/y34_f50.html
You could also use the Z33/V35 rear spring delete for full coilover conversion and additional toe adjustment (to allow more camber from the camber arms).
Or you can weld on some thread for rear spring bucket adjustment
OR (and probably the easiest method) is to fit offset bushes to the rear upper arm.
(i think its these) https://superpro.com.au/find/superpro-performance-handling-kit-for-a-superpro-suspension-parts-and-poly-bushings-for-nissan-350-z-z33-2003-2009-/productnr-SPF3321K/cid-999501121/vid- https://superpro.com.au/find/superpro-performance-handling-kit-for-a-superpro-suspension-parts-and-poly-bushings-for-nissan-350-z-z33-2003-2009-/productnr-SPF3313XK/cid-999501121/vid-
Also, you said you have rear camber arms, but what about rear toe arms? its a must-have with camber arms because the camber arm adds just as much toe as it does camber....