Nope, knuckles on a z32 are cast alloy while skylines and silvias are cast iron. Only difference is the shock mounting point between the two. Its possible to use one on the z32 but is a downgrade due to the higher unsprung mass.
I was actually thinking could you go the other way.. I have 4 pairs of 300 ones here and wanted to see if they would go in my R33
It's not uncommon for the silvia and skyline guys to use the z32 rear knuckles. You'd just need to do something to get the shock to bolt up to the knuckle right.
Hi, make sure to use a hicas knuckle on the r33 if it has hicas (most usually are) the 300zx uses a fork type coilover mount like the gtr, while r33 is eyelet. however it is possible to use r33/34 gtr rear coilovers and then the knuckle will be a straight bolt in.