I now have a very stock '79 280zx. I have noticed that the stock differential is a one legger and i would like to know if there are any companies that sell a limited slip differential.

 

Nissan Motorsports and Motorsport Auto sell them. They are about $700-900.

Or you can buy a factory R200 LSD unit from a wrecking yard. They came only in the 1987-89 300ZX turbo. They are a 3.7:1 gear ratio. Your car probably has a 3.54 gear ratio. You'll actually have more torque with the lower ratio but you'll need to use the speedometer cog from a different Z to calibrate your speedometer correctly.

 

is the factory r200 viscous lsd?

 

R200 refers to the design of the differential and the width of the gearsets. R200 does not mean that it is LSD. (just to clarify)

1987-89 300ZX have an R200 3.7 ratio. The turbo models only have the same "type" of diff but with LSD

1988 white "special edition" 300ZX turbo comes with an R200 vicious LSD. Only a little sticker on the diff designates it. It is not a bolt-in swap though so you should actually avoid this one. The half-shafts are slightly different. If you're looking for a challenge and want this type of traction control, then go for it.