im not sure what you are after
you obviously are after the vspec turbos? Vspec skylines are GTR's RB26DETT.
The R32 RB26DETT has the same turbo vspec and non vspec
The R33 RB26DETT has the same turbo vspec and non vspec
The R34 RB26DETT has the same turbo vspec and non vspec
That said, GTR turbos are not a suitable upgrade for an RB20DET. They are too small.
The info is there on the forum, but i cant be bothered looking for it. Just do a search for R32, R33, R34 gtr turbo or something like that