The grates for the stove were in pretty good shape except for the bits that were positioned directly over the flame.  There the porcelain enamel was gone and the exposed metal had begun to rust.  I considered painting those parts with high temperature paint.  But that paint is not meant to withstand the temperature of direct propane flame.  Instead I decided to have the grates completely re-coated in porcelain.  The company I chose was Independence Porcelain Enamel in Missouri.  I think they did an excellent job.  The re-enameled grates look GREAT!  Should be good for another 50 years.