all depends on your current set up. if not currently fitted with P/S then you will need box, pump, brackets and maybe new crank pulley
also the steering boxes are handed a LHD will not fit a RHD but CJ and early XJ are interchangeable, as for the pump recently found that the Mk1 Renault Clio 8 valve is fitted with the same pump (£16 delivered from ebay) although it is cranked over by about 15 degrees, this is not an issue if your doing a conversion as would probably be easier to make a new bracket than find a cheap CJ pump