I have no experience reconditioning a worn cast iron pump by applying a rubber liner. All of our rubber lined pumps were originally manufactured with the rubber liner. For an existing pump, it would be necessary to apply a coating over the eroded/corroded surfaces. I believe that there are coatings available that could do this. The only company that I am familiar with that might make suitable coatings is Belzona. As long as there is room to apply the coatings without interference between rotating and stationary parts, it should be possible. I suggest a Web search for Belzona, Rubber, Coating.