Reproduction Of Original Correct Foam Seals To Rebuild Heater Box For Cars With Air Conditioning Only 1966-1967 Chevelle heater box seals are a critical replacement when working on any A-Body heater box. These Chevelle heater box seals create an air-tight seam among critical heater box components. Using low quality or used heater box seals will lead air leaks and degrade the performance of your Chevrolet Chevelles heating & air conditioning systems.