Part Type: HVAC Heater Core. 2007 GMC Sierra 2500 HD Classic Submodel: Crew Cab Pickup; Engine: 6.0L V8; w/o Rear Vents In Center Console;. 2007 GMC Sierra 2500 HD Classic Submodel: Crew Cab Pickup; Engine: 6.6L V8; w/o Rear Vents In Center Console;.