Nige,
sort of simple. That's what I had with my ARB, just put a 4.7 R&P on it with a spacer ring behind the ring and swapping out the pinion.
but... the stock R&P didn't even last two punches!! 4.7 seems fine with an open diff, I've been running them with my Simex for over a year no bother, but lockers just let you get more torque to the wheels and stress the components far more.
By all means try it but I'm now running that stock diff (thanks) while I save for a set of 4.75 R&Ps