I haven't seen the V160 and R154 side-by-side, but, knowing the R154 fills the entire tranny tunnel of a 240Z and a V160 fits, I can't imagine the V160 being much larger (wider, anyways).
The turbo MKIV Supras come with a 3.13 rear end, but they have slightly taller tires and they weigh about 800lbs more than a 280Z. I have a LSD R200 with a 3.15 to run with my R154; the 3.15 is very rare, FYI. I think a 3.36 would be fine, too. The R230 is always an option, as well. Here is my thread about the ratios I have to work with: http://forums.hybridz.org/showthread.php?t=134484