hot truck

my 86 mazda B2000 runs cool in the winter and it sucks i changed the thermostat and still no dice what can i do to make it warmer without overheating?

put some cardboard infront of the rad to block the air flow play with the size till you get to were your truck is worm but not overheating or get a differnt temp thermostat to a differnt one thay have differnt temps at what thay open might wont to look into flushing your heater core might be cloged to