84-89 had an r230, and you'll have to redrill the moustache bar and fabricate mounts for the front crossmember. the r200 with 3.9 gears came on 77-83 z cars, i believe. it was on automatic 77-78 280z's

 

That's not the information I have heard. I'm not sure on the 84-89 300ZX. I know the 87-89 Turbo 300ZX has a LSD R200 that you can bolt in.

But the 3.9 is found on only the 1981-83 280ZX non-turbo with a manual transmission. The 1976-78 280Z has a 3.54 in both the manual and automatics. The 1979 280ZX has a 3.7 the 1980 has a 3.54 in the n/a and a 3.54 in the turbo. The 1981-83 280zx turbo has a 3.54 again.

automatics are more rare, so it is very likey you can find a 280zx from 81-83 with a 5-speed originally.

 

actually, i think bleachzee is right, i think i gave wrong info. it's the z32 that has the r230, along with the infiniti q45