03 Honda civic 1.7 Ex head gasket replacement

I’ve had a constant overheating problem with my engine and I’ve replaced the radiator, water pump and timing belt, and thermostat twice. Even after replacing all of this it still overheats so after looking online I figure it can only be the gasket. I haven’t noticed a problem with coolant in the oil or white smoke. Also right before it overheats I lose heating in the vents.

My question is is it the head gasket or could it possibly be some other obscure problem. Also the car has 325,000 miles.