I hope you are not using coolant without mixing it with 50% distilled water. Using pure coolant will make the engine overheat. It has to have 50% water mixed with it (unless you bought pre-mixed coolant). I also hope you are adding coolant directly to the radiator; and not just to the reservoir bottle. When a radiator is drained; the siphon action between the radiator and the reservoir will be broken. It will only return after the radiator is completely full and free of air. Until then; the level must be topped up directly at the radiator. If the radiator pressure cap does not hold 18-22 psi (which is a much higher pressure than the older Dodge engines used) it will lead to overheating.
I would also have your cooling system pressure tested. Without applying pressure to the system; there is no other way to tell whether you are getting leaks after it heats up and is running at speed (which is when the pressure builds up). Many leaks only occur when the pressure is high. And don't forget that the heater core (and the rear heater core and rear water pump; on vehicles so equipped) can also develop leaks and cause overheating.
If you have the 5.9L (360ci) engine; the distributor may have been timed too far retarded. This can lead to the engine overheating. The 5.9 engine can also be used with a choice of 160 degree, 180 degree, and 195 degree thermostats. If you have the 5.9 engine, and the ignition timing is set correctly and it still is overheating: I would strongly suggest using a 160 degree thermostat.
The 4.7L (287ci) engine does not have a distributor, and can only be used with a 195 degree thermostat.
If none of these things help; then either the radiator is clogged to the point where it will not flow enough coolant to keep the temperature normal; or the thickness of the radiator core is not large enough to dissipate the amount of heat needed to keep the engine cool at this age, with the fuel octane you are now using, in the climate where you currently live. It is not uncommon to see vehicles which have radiators that are too small for the service they are used in. Aftermarket radiators are made for your vehicle with many different core sizes, for that reason.