Unique auto sport in Australia did something like that. Check out their project 300zx Page #2 for more details.
"Here we are replacing the factory R230 viscous coupling 3.7 with R200 R32 GTR 4.3 Nismo mechanical lock clutch pack diff with a modified 300ZX non turbo cradle (no hicas to worry about!) with alloy spacers for drive shafts and tailshft to suit Nismo diff mounting bushes and urethane cradle bushes. As a bonus the 300ZX diff weighs 52kg whilst the new GTR diff weighs 36 kg."