Why does your Chevy 305 Temp gauge read all the way to right and heater stop blowing hot air and car is NOT overheating?

Sounds like you possibly have trapped air in the system. Bleed all trapped air form the cooling system. Jack up the front of the car, and remove the radiator cap. Fill the system to the top with coolant and start the engine. Let it run until no more air bubbles are escaping. Keep it full while doing this. Also look for bleeder valves and use them if equipped. Funny thing, one side of the car was overheating. The trapped air theory seems to have been correct. I'm assuming the the gauage was all over the place because it WAS hot, and then the rush of water came in and cooled it off. Too bad I didn't figure that out sooner. I checked all of the cylinders for leaks after it overheated and found that #4 and #6 actually squirt water out of the spark plug hole. I have ceased driving the car and will fix the head gasket tomorrow first thing (hope the head is okay).