1998 dodge dakota. takes to long too warm up. already changed thermostat
I'd suspect the thermostat again. But I think you radiator core is partially blocked and you had overheating, so the need for a new thermostat.
It doesn't help to replace the thermostat alone, most modern thermostats have a composite metal alloy retaining the spring, so when the radiator overheats the alloy fuses over and releases the spring, completely opening the flow of cooling liquid.
One of the symptoms of radiator blockage may be a non-operating interior heater (it's also clogged).
One way to test the radiator for blockage, is to start the truck cool, let's say first thing in the morning, and carefully put your hand on the radiator fins, moving along the surface, as the motor starts heating. If you detect a mix of warm and cool zones, your radiator is clogged.
I'd recommend you first change ALL of your hoses (ALL means ALL of them, including heater, A/C, etc), then do a cooling system flush, then drain completely the system and try to force water to clean debris in the system, then blow compressed air to flush the remaining liquids.
Now, change the main radiator and the heater radiator, install a new thermostat and fill it with NEW (check the dates) liquid coolant.
If you're doing your own mix, use only distilled water; even if the system is a closed circuit, minerals in the few gallons or quarts of water can interact with aluminum parts in you motor.
Since you'll be removing the radiator, I'd check also the water pump seals, it may be worth to change them, even if they are not leaking; water pump seals and gaskets are a common problem with Dakotas and Durangos.
Hope this helps.