To fit the slipper you need part number FF054. This is the driveshaft that is threaded at the end to allow adjustment of the slipper clutch tension. The part all 4wd trucks have is milled with a flat spot to enable the drivecup grub screw to grip. I am having a bit of trouble locating one of these driveshafts at the moment. It seems single speed Fun Factors are not too popular anymore!! Might give CEN direct a try. Personally I think I will need the slipper clutch fitted as running on the beach could be hard work on a dirct drive!