If you are using 100% undiluted coolant in this motor; that would make it overheat. Coolant is designed to be mixed with at least 30% water (preferebly distilled water) in order to properly transfer heat from the engine to the radiator.
If the radiator cap has less spring tension (holds less pressure) than the original cap did; or if the rubber seal on the cap is damaged or worn; this could cause overheating; as the cooling system is designed to operate under pressure; in order to raise the boiling point of the coolant. If there is only atmospheric pressure in the radiator (due to the radiator cap not holding pressure) the coolant will boil under some normal operating conditions; which will create turbulence and bubbles in the coolant that eventually leads to overheating
If the thermostat was installed upside down (with the spring on the side away from the engine); this would lead to overheating.
If the radiator cap was not removed (when the motor was cold) to check and refill the coolant level on several consecutive days after each time the cooling system was refilled during a repair; it is very likely that the trapped air (which always is found in the system after it is refilled) worked its way to the top of the radiator and interrupted the siphon action between the radiator and the coolant reservoir bottle. When this happens; the coolant in the reservoir will not flow into the radiator when the radiator coolant level drops; so the radiator level can become very low while the reservoir remains full. It is only after all the trapped air works its way out of the system that the level in the reservoir can be depended on to indicate whether or not the radiator is full. And if anything happens to introduce air into the system (such as a hose leak or a leaking head gasket) the siphon between the radiator and the reservoir will be broken and there will be no external indication of the radiator level after that time. When there is ANY doubt about whether the radiator coolant level is all the way to the top; the radiator cap MUST be removed (when the motor is cool) to check and top up the coolant.
If the ignition timing was checked and adjusted without first following the manufacturer's instructions for temporarily disabling the electronic spark advance circuit; the timing will come out grossly retarded. From that moment on; the car will experience engine overheating, reduced performance; and reduced fuel economy. All too many mechanics and smog inspectors make this potentially disastrous mistake!!!!!!! You cannot trust ANYONE to check or set the timing properly on cars with electronic distributors like yours (unless they assure you that they first disabled the electronic advance).
Finally; the 1993 Camry V-6s were plagued with engine design problems. There were several unsuccessful factory fixes; but the factory eventually redesigned and replaced the motors in all the affected vehicles which came in. At that time, Toyota dealerships were jammed with Camrys waiting for engine replacements. But not all the V-6 cars came in for a new motor. If your car has a V-6 and was not one of the ones which got a new motor; you may now be dealing with the reasons Toyota gave up on that engine design.
Furthermore; if your motor has ever significantly overheated for ANY REASON (regardless of whether or not the engine was replaced); there is a substantial likelihood that the cylinder heads have warped. This typically causes the head gasket to allow coolant to leak into a combustion chamber and blow it out the exhaust (which causes repeated coolant losses); or to leak compression pressure into the cooling system and cause uncontrollable overheating. Radiator shops and some garages have testers which can determine whether the head gasket leaks
Thank you for your patience. This could not have been adequately explained in fewer words.