Strange..... My IS200 has an RS200 LSD fitted,, no difference in final drive with IS200 LSD. There were two differences though: no cooling fins on the Altezza diff-housing, and I had to use the old axle stubs as they are 6-bolt on the Tezza instead of 4-bolt on the IS200.
From the pics above there must have been quite some variations, only you wouldn't get to 146 mph with a manual RS200 and a 4.3 final drive, with a 3,909 you would.
Maybe someone can complete the gaps in this story
Cheers,
RX-Men-8