Part time 4wd conversion

Hello
I have an LT95 Range Rover gearbox that I am going to fit into a Series 2B Forward Control Landrover (in order to have a stronger gearbox)I wish to convert this Full Time box to Part Time 4wd.I intend to modify the centre diff along the lines of removing the planet wheels and weld/bolt the rear prop sun wheel to the carrier.The only problem I can see is supporting the rear end of the front output shaft where it enters the diff.Without the planet wheels there is nothing to stop the front sun wheel floating back towards the rear one,it would need some sort of spacer in between.Also I don't know if this front sun wheel would last if used as a constantly turning bush/bearing.I know this conversion has been done as I spoke to someone several years ago who had done it himself.Does anyone have any ideas about how to support the rear end of the front output shaft?Any ideas very welcome.Thanks a lot