No
Nay
Not all Z31s had LSD. Actually it’s hard to find them with the LSD. Viscous LSDs work fine for drifting. Theres a tiny difference because the locking action is a slow progression, but you probably won’t see much of a difference unless the disks inside of the VLSD are severely worn and the fluid won’t lock as hard anymore.
One thing that you must be aware of. Though they are all R differentials that you are talking about, they do not bolt up exactly the same. The output stubs and halfshafts are the major concern. I don’t think between all the sizes the output stubs all had the same number of splines. R160, R180, R200, and R230 are different… Actually most R200s are the same as R230s. The R230 is only found in the Z32 TT and you must get the entire rear subframe to mount it (the subframe had an undesirable HICAS setup)
The most common rear end swap (on 510s and S12s) is the diff plum from a Subaru… They used R160 and R180 ring gears. Most of them were LSD and they are easier to get a hold of in scrap yards. Early 80s to mid 90s used the same diff (commissioned by Nissan). I think the Subaru model to look at is the XT or something?? Don’t remember exactly. I’ll have to look up more info for you.
EDIT – I Found some more info for you. At dimequarterly which has millions of writeups about 510s
on the left side in Technical Department click " Drivetrain". Then click on the link that says “Subaru LSD Differentials”
You will end up here:
http://kmhafer.datsun510.com/Subaru.htm
Reason I gave you the first site (dimequarterly) is cause it has tons more info on engine swaps. KA, VG, SR, FJ… Anything you want into a 510. It’s not the same car but it’s very similar.