318 hesitation when cold

Normal. When the engine is cold, the bimetallic spring strip in the choke thermostat will try to close the choke. Once the engine starts, the choke pull-off will fight this and hold the choke most of the way open. This is connected to manifold vacuum. If you suddenly open the throttle, manifold vacuum will drop to zero, and the choke pull-of will relax allowing the choke plate to close a little (air flow will keep it from closing completely, it'll just swing loose). Now, as the engine warms up exhaust is heating the choke thermostat in the manifold, causing it to stop trying to close the choke. So, after the engine has run for 2-3 minutes the choke should be vertical and stay there until it has cooled off for several hours.

To verify this, with the engine stone cold, not running, if you press the gas pedal to the floor (or open the throttle by hand) the choke plate should close completely, and the fast idle screw should be on the highest step of the cam. Now if you crank the engine it should start and the choke pull-off dashpot should open the choke most of the way. If you tap the throttle the fast idle cam should drop until the screw is on the lowest step (1100-1500 RPM). A factory service manual, or the instructions in a carb kit will show you how to set and adjust the choke and pull-off. If it needs to be adjusted, it's because somebody monkeyed with it.

You do have the air hose between the divers side exhaust manifold and the air cleaner snorkel right? Also make sure the flapper in the snorkel is closing when the engine is cold.