If the OEM utilizes the combination of a rubber gasket and polyurethane as a retention system, an equivalent adhesive bonding system shall be used in the installation. In cases when the OEM did not include polyurethane or an equivalent adhesive system, such systems shall be used if later production models included the addition of adhesive systems without body style modification. If the OEM gasket installation did not include adhesive and the vehicle is licensed for highway use and is less than 10,000 pounds gross vehicle weight, the installation shall include polyurethane or an equivalent adhesive bonding system. The following vehicles are exempt: Registered as a Class L historic vehicle; Registered as a Class N street rod vehicle; and Registered as a Class K farm area/island vehicle. When sealing air or water leaks within a rubber gasket or polyurethane adhesive system, only compatible polyurethane shall be used. No silicone or butyl may be used.