I would go thru the proceedure listed on your emissions lable located on the right front side by the radiator support bracket. You first need to make sure it is timed correctly. All adjustments are with a normally warmed up engine. Also check that your heat control (some call it a heat riser) is functioning properly. That is there especially for cold start.
Another cold weather control is the air intake. The vacuum motor inside the scoop determines if air off the heat schroud or air from the front scoop ot mixed air enters the carb. It is usually controlled by a Cold Weather Modulator (CWM on the emissions diagram) and Bimetal valve. Both are usualloy mounted on the filter housing.
A sample emissions attachec. The one I am using for my 351W.
Basically I had the same problem because none of this was on the engine when I got the truck. Most everyone said put a manual choke on it, I didn't because that would only be a partial fix or bandaid. The end result was an engine that wouldn't let the truck move untill it was completely warmed up to a start and go engine.
OK enough bla, bla, bla :blush:
Good luck,
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