TYC HVAC Heater Core. 1975 GMC K25 Submodel: Base Cab & Chassis; w/o AC;. 1975 GMC K25 Submodel: Base Standard Cab Pickup; w/o AC;. 1975 GMC K25 Submodel: High Sierra Cab & Chassis; w/o AC;. 1975 GMC K25 Submodel: High Sierra Standard Cab Pickup; w/o AC;.
