We looked into this a year or so ago and decided to go with a P38 box mated to a disco 1 ps pump and housing. P38 fluid res and all hoses. Had to get a custom high preshure hose adapter. P38 track rod. All parts where about 700.
Works like a charm with effortless steering wheel movment.
------ Follow up post added June 23rd, 2015 12:10 AM ------
Additionally We had to fabricate a V pulley as we coulnt use the serpentine pully on the disco pump.