TT models are R230's. They are bigger and stronger, but the R200's, which you already have, are plenty strong for most setups. The R230 is not a direct swap, and it has a considerably taller final drive. The NA Z32 uses an R200. It's not a direct swap, and if you already have the LSD, you are gaining nothing.
The 280ZX did not come with a limited-slip from the factory. I just looked through the factory service manual to make sure, and all its differentials are open 2-pinion varieties. It also has a completely different housing and output shafts than the later cars. The first Z with LSD of any sort was the '87 300ZX turbo, which had the clutch LSD. They later (unfortunately) switched to the VLSD, although some more recent models got a helical LSD, like the S15.
