I want to know if they are any differences in the internals of the USDM and JDM GSR gearbox.

I am asking since where i am from all the cars are RHD imports from Japan. My EG is also one and i have a JDM B18C motor and gearbox in the car. The Final drive i presume is a 4.4 and since i have cams and higher compression the car likes to be in the higher RPM and i was thinking of buy a 4.7 final drive ( or i see OBX has a 4.9 final drive) and installing. But i want to know if they will fit.

Or do i need to buy extra parts inorder to install with out any hassle