From inside (document excerpt):
Coupling Box Kit Cancels: IIK 340M-40-30 IIK 340M-40-39 6-98 Installation Instructions Part No. 320721-761, -762, -763, -764, -765, -766, -767, and -768 NOTE: Read the entire instruction manual before starting the installation. This symbol indicates a change since the last issue. SAFETY CONSIDERATIONS Installing and servicing heating equipment can be hazardous due to gas and electrical components. Only trained personnel should install or service heating equipment.
Untrained personnel can perform basic maintenance functions such as cleaning and replacing filters. All other operations should be performed by trained service personnel. When working on heating equipment, observe precautions in the literature, on tags, and on labels attached to the unit. Follow all safety codes. Wear safety glasses and work gloves. Have a fire extinguisher available. Recognize safety information. This is the safety-alert symbol. When you see this symbol on the furnace and in instructions or manuals, be alert to the potential for personal injury. Understand the signal words DANGER, WARNING, and CAUTION. These words are used with the safety-alert symbol. DANGER identifies the most serious hazards which will result in severe personal injury or death. WARNING signifies a hazard which could result in personal injury or death. CAUTION is used to identify unsafe practices which would result in minor personal injury or product and property damage. Turn off gas and electrical supplies to unit before beginning any installation or modification. Follow operating instructions on label attached to furnace. Failure to follow this warning could result in electrical shock, fire, personal injury, or death. Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and dangerous operation. INTRODUCTION This instruction covers installation of the coupling box kit Part No. 320721-761, -762, -763, -764, -765, -766, -767, and -768 in multipoise, 40-in. tall, condensing gas furnaces. NOTE: A releasing agent such as PAM cooking spray or equivalent (must not contain corn or canola oil, aromatic or halogenated hydrocarbons or inadequate seal may occur) and RTV sealant (G.E. 162, G.E. 6702, or Dow-Corning 738) are required before starting installation. DO NOT substitute any other type of RTV sealant. G.E. 162 (P771-9003) is available through RCD in 3-oz. tubes. Table 1–Kit Usage UNIT KIT PART NO. 320721-761 320721-762 340MAV 350MAV 490AAV