Ok guys I have searched my behind off!! Either I am blind or just cannot find out the ring gear size of these cars...Anyone?? thanks!!!

 

it has an r200 diff so it should be 200mm or 7.88". Thats all i can find on the older r200, seems no one ever knows anything about the 350z or is willing to share it.

 

Hmmm, thats seems a little on the small size for this car...I mean the s-2000 rear is a 7.5" and its weak as hell....Thanks though...Can anyone else confirm???

 

There is a bigger one the r230 its bigger than a ford 9inch but only found in the 300zxtt.

Here is some information on nissan diffs, this site has quite a bit on them but i can still find nothing as to what ring and pinions gears will interchange with the 350z diff. http://forums.hybridz.org/showthread.php?t=103512

Found some more information.

R160 = 160mm or 6.29” in diameter
R180 = 180mm or 7.08” in diameter
R190 = 190mm or 7.48” in diameter
R200 = 200mm or 7.87” in diameter
R230 = 230mm or 9.05” in diameter

R160 - Originally came in 510s, Subarus. Lighter weight than stock Z diff
R180 - Came in 240, 260, 77-78 280Z automatic, and 280ZX automatic, among others. Also in the new WRX STi
R190 - Nissan Comp diff used in early 70's race cars and 432R's. Still some of these floating around.
Longnose R200 -weight 76 lbs - Came in 260Z 2+2, 280Z manual, 75-76 automatic and 2+2, Z31, 200SXT
Shortnose R200 - weight 72 lbs - Later model 240SX, Q45 1989-1996, R32 Skyline, 300ZX NA, 350Z
Shortnose R230 - weight 114 lbs - 300ZXTT, Armada front diff

 

Thanks for all your research and help .. I tried searching for like a straight hour and still could not find concrete info on this myself..