I have a costomer that has a 1983 RRBD seires Rheem 3 ton package unit.The unit is set up for natural gas and would like to convert it to propane.This unit has never been started,IT looks like brand new.The local dealer hasn't been any help saying its to old to find any literature.Is there a web site that might help me find parts needed for the conversion.Any throughs would be appreciated.