Nothings been confirmed as far as I know but I think S13 LSD's for the Pre-facelift model should work with minimal modifications and I'm pretty sure someone is running an S14 diff, again, with limited mods/scavenging required.
I've been trying to get hold of some output shafts to compare them with standard S12 ones, but no one's been willing to part with any when I've asked around
