Your truck has/should have a manual choke. Passenger car carburetors had automatic chokes after 1949, so if you have a passenger car carburetor without a manual choke conversion, you will have trouble with cold starts, and maybe low speed operation. Your late-model passenger car carburetor has an automatic choke that won't work without the stove on the exhaust manifold and the heat pipe to the choke housing on the carburetor. Does the stalling problem improve or disappear when the engine gets to normal operating temperature? If so, you have a carburetor heat matter to resolve- maybe the heat riser valve is not working properly. If the problem persists or worsens as the engine gets warm, the carburetor may be getting too hot- heat insulator under the carburetor is missing. Memory is foggy on that matter, but most 6-cylinder engines used an insulator of some sort. As mentioned by others, the base gasket may be blocking a vacuum passage, and causing the power circuit to be continuously fully open. That condition will give you poor idle and low-speed operation, which can be concealed by pulling the throttle a small amount as you indicate you are doing.
Harvester
