So my dad and I replaced the thermostat, outlet housing, and radiator within the past month (all went bad at once) So ever since replacing the system, we have been noticing that as we put coolant in the system, coolant continues to leak through the overflow hole at the top of the overflow tank. I know it's supposed to be a sealed system but continue to think that air is getting in the system allowing more pressure to build and push the coolant to the overflow. I know it's not the head gasket as the oil is fine and no signs of water/coolant in the oil. What else could it be???
As fred_dot_u stated, the reason your car's coolant is overflowing as it is is due to the radiator cap no longer functioning properly. My sister's car, a 2004 Dodge stratus...same vehicle, was in to a mechanic recently for engine performance issues, however, the mechanic also noted that he, for whatever reason believed the engine was overheating when it was not and claimed the boiling over coolant was a result of that. In reality what was occuring was that the coolant was absorbing more heat from the engine after it was turned off and, unable to maintain the pressure normally required by the cooling system, was overfilling the reserve tank.
All in all a radiator cap replacement should fix your problem as it did on my sister's. Best of luck to you.
Those cars are notorious for head gasket failures, and depending on the leak location you may not get water moving into the oil. The cylinder pressure even before ignition is about 10 times higher than the coolant pressure, so the tendency is for combustion gas to leak into the coolant, forcing coolant out through the overflow.
You also could have an air pocket that wasn't been completely removed when you refilled the system. Many of the Chrysler vehicles of that era required an additional accessory to be attached to the top of the coolant reservoir when you filled it in order to build enough elevation head to push the water into all of the air pocket areas.