you asked for a kit. I am telling there is no real kit to speak of. A kit in my eyes would include the following 1) Turbos 2) Lines 3) piping 4) Manifolds 5) a support structure.
Greddy does not sell a kit for the 300ZX that includes TD06-20G turbos, They do sell it with a set of TD05H-18 turbos though.