well what you have are afew opions a fj20 gear box will bolt up to it but trying to find one that is!!! Another thing you can change the front half of of the gear box (bellhousing) to suit a r30 skyline box you have to change a bearing in side the box its not hard to do i used an NA fj20 bell housing. I dont know if they are the same as the Z18t gearbox but and fj20 bell housing will bolt upto an r30 skyine gearbox