getting warmer

have a 88 5.0 ford truck sitting the temp gauge starts going up. changed the heater core new one ran colder, but now sitting it starts climbing again even driving it stays around a 1/4, never have changed the thermastat new cap on radiator, has a big aluminum radiator looks clean inside never changed the water pump eather.
don't know witch thermastat kragen site shows a 160-180-195 the truck has everything air all power if that helps. any ideas thanks
jenn

okay go with the 195 but change your fan clutch mine was doing the same thing changed it and problems went away