Sorry to say but this is a common symptom with a blown headgasket on your car. You can verify that the headgasket is bad by performing a combustion gas leak check. The tools to do this can be purchased for about $50.00 It basically involves sucking fumes through a liquid at the radiator cap and looking for a change in the color of the liquid.
Without performing a combustion leak check you cannot verify that the headgaskets are fine. The compression from the engine can be pushing air into the cooling system. This air can create a pocket behind the thermostat which would not allow it to open and thus cause an overheat problem.
It's also possible to have a cracked head. Depending on the quality of the rebuilder, they may have just installed some new gaskets and never checked the head.