Hi mate sorry i cant help but im keen to do the same thing to my cefiro back in kiwi land. A few of the drifters here are running them.
ive done a fair bit of looking into this but haven't really found much info. Theres a 5 speed jerico box available which imo would be the best option http://www.jericoperformance.com/5speedroad.htm.
Ive come across these guys as wel http://www.hpracing.com.au/ would be the best bet to talk to, im sure they would help. I will post more if i find out