There is absolutely no reason why this can't be used on the 4wd, the issue of the concentric slave is no biggee, the front bearing housing/nose of the box may not fit from the kit, but your existing one could always be lathed down or built up with a tube to match the size needed for the slave, IF different to the 2wd ?, then it is a case of fitting a long stud in place of one of the bolts holding it on, the slave uses this as a steady, to stop it rotating.
On the 2wd I had to use the new nose/bearing part as it was a different diameter, just had to reduce the diameter of the flange part by 1.6mm to be a snug fit in the bell housing aperture, and take 10mm approx off the end.
I welded up the slot in the bell housing on mine, then drilled two holes for the pipes, feed and bleed(remote), I then made a little bracket that bolts under a bell housing to engine bolt above the starter for the bleed screw, the kit appears to suggest the bleed is fitted on the slave itself!!, but I didn't do it this way.
The actual slave is part of a kit made by RAM RACING, in the us, RAM 78130,78132, so some good comes from the us apart from all the TRACI LORDS videos I have!!
I have been out in the car today to drop off some rubbish down the local tip, old paint tins crap this crap that all went in the boot of the cossie, and a old plastic table and chairs etc in the boot, the hydro is a revelation compared with the std cable set up, where most of the effort is used to overcome cable binding, due to the teflon liner rucking up.
tabetha