Gas Conversion Kit Natural-to-Propane for 90% Step Modulating Variable Speed, Condensing Gas Furnace Part No. KGANP4301STM to convert the following furnaces from natural gas usage to propane gas usage: Models 58MVC and 355CAV 4--Way Multipoise, Hot Surface Ignition, Variable-Speed, Step-Modulating, Condensing Furnaces. This kit is designed for use in furnaces with 60,000 through 120,000 Btuh gas input rates.