Don't rule out the possibility that your catalytic converter is plugged due to age. Before you throw more money try asking your question at www.dodgetalk.com or www.allpar.com for Mopar vehicles [Dodge Chrysler Plymouth etc.] The P1280 code has to do with throttle position but that shouldn't make it run hot. Or even consider taking it to a Dodge/Ram dealer who specializes in your vehicle. You will spend less time and money than if you try hit or miss replacing parts at the corner mechanic. Tell them you want to fix the cause of the specific problem, not rebuild a 14 year old vehicle. You must manage the service advisor, Listen patiently then tell him/her you want to repair the exact cause of the overheating and will return another time for the laundry list. Don't be intimidated, manage them!

it could be the water pump, maybe the cooling system needs to be flushed out, especially the radiator ! it might be the fan not kicking on or if your getting any codes it might be the coolant sensor !

Use some tools to read the codes, and then diagnose your engine and ecu, you can find these diagnostic tools from http://www.obd2life.com

Are you loosing water? Is your fan working? Have you checked the radiator?