What do you want to use the car for? Still running the NA motor?
The 4.083 ratio is really nice I wouldn't want to give that up for any of the longer ratios unless you went to the 6 speed box. Spec R is a torsen type and it's good for grip poor for drift, comes with ~3.7 ratio. You could pick up just the centre for very little money from Yahoo auctions and throw it in the Spec S pumpkin, you need the output flanges too afaik. R32/33(non v-spec) GTR centre is quite a nice mild 2-way that's totally streetable and will fit in the Spec S case with the original output flanges. I ran this setup in mine for a while and it worked quite nicely. It did still do the occasional one wheel peel though so I decided to install the nismo 12kgf overhaul kit. This is really made for a nismo LSD and the stack height is wrong so I had to have shims made up to get the preload right. This setup I feel would be ideal for someone wanting a drift car for the street, there is no tyre skipping or chatter from the diff, however it is very agressive with the lockup on throttle despite the mild 45 degree ramps. Honestly it's too tight for me now, it understeers on the way in and oversteers on the way out, handling was a lot nicer before for fast road grip driving.
Of course, if road manners are not a concern then you've got the likes of Nismo GT LSD, Kaaz, Tomei Trax etc..
Definitely though, I would not put a longer gear ratio into a car with the NA engine, they are sluggish enough already.