heating issues when idling 340 73 duster

Thanks for all the suggestions guys, haven't been back on because wife had a tumor taken off her petuitary gland and then developed blood clots in her lungs. She's doing well now. My biggest problem with the car is is i have no idea what has been done to the motor. It was "rebuilt" by the person before the one i bought the car from. One thing I do know is it is over cammed like most. Sounds nasty at idle but is doggy on low end even with 3:91 gears but really comes to life around 2500-300 rpm. The other thing is I don't even know if it has a thermostat in it (i know, that's easy enough to check but have been preoccupied lately). Probably my first things to do are check thermostat and timing and see where it goes from there. Thanks again for all the suggestions.