'75 International Truck puzzler
 

My truck has an International 379 v-8 which runs great except it hates to start in the cold For some reason it will not start below 20 degrees. New ignition, wires, plugs and new carb but nothing helps except heat. Left inside, starts right up. Seems to have spark and gas, no water foundbut itrefuses to fire when very cold. Anyone have any ideas? Thanks.