A week ago my car overheated and the heat was cold

That really wouldn't help. The reason that engine has bleeders is because it traps air in it. The only way for the air to get out is through them. The only good repair would be doing the head gaskets or swapping out the engine. Swapping is tricky though because GM used a few different control systems on that engine over the years. If you don't get one with the same system it won't run.