OER Parts offers a wide selection of Heater Parts for your 1984 GMC All Models. OER Parts offers 1984 GMC All Models Blower Motor, 1984 GMC All Models Heater Box, 1984 GMC All Models Heater Control Valves, 1984 GMC All Models Heater Cores. 1984 GMC All Models Hoses and Parts, 1984 GMC All Models Vent and Duct Parts.