120V Carb heater
 

So the point of a block heater to improve economy is to get the engine into closed loop quicker.

My '84 Volvo 244 knows nothing of loops, as it has a Zenith side-draft carburetor. Given that my commute is 4 miles each way, I am guessing that there could be a massive benefit to wrapping some 120V pipe heater tape around the carb and plugging it in for an hour before I leave for work, along with the old space heater I am already using to pre-heat the cabin. Especially on these 30-40 degree mornings. I would be great if I didn't have to pull the choke.

does your car have a coolant line that keeps the carburetor from icing up? if so that might be the best way to heat it if you don't want to have a block heater, if you do have a block heater then the heat should heat up the carburetor as well.
The use of the choke is not because the carburetor is cold but more so because the combustion chamber is cold, again, a block heater will help a great deal with this, warm fuel might not hurt but if you get the fuel to warm it's going to cause it's own problems and you are heating such a small area that a 6 foot chunk of 120v heat tape would be over kill so you could get away with cutting it down to 1/10th that and run it off 12v, 6" of heat tape should be just about right to keep the fuel bowl warm.

I still run carb too, but with no choke.
That is not a bad idea. I have considered using a 40watt halogen cylinder bulb placed next to the carb to keep it a little warmer over night.
So far I have only used the heat gun in the morning to get the car fired.

I'm not sure a 40 watt bulb would be enough unless you wrapped the carb with something and put the bulb inside. That might work.

Is the choke really for the cold combustion chamber? I thought the choke is necessary because cold fuel is very unwilling to atomize and when a carbureted engine is "warmed up" and runs good, it is because the temp of the carb (and the fuel inside it) is warm enough from easy atomization to occur. But I could be wrong.

Oil pan 4: what do you warm up with the heat gun, the carb? And no choke is necessary once you do this? The answer to that will solve the "what the choke is really for" question above.

In the winter the gasoline stays pretty cold, even on a long trip because the gas tank is hanging right down in the open and the carburetor tends to stay cold because of the cold fuel in it and the veturi effect of air passing through it causes it to cool, that is why it often has a small amount of engine coolant running near it, to keep it warm once the engine warms up, so it doesn't ice up, but that takes a while to.
A sure fire way to get a cold engine to fire up is to pull the spark plugs and heat them up, once those droplets of gasoline hit the warm spark plugs in the combustion chamber then it turns to vapor and will burn, the choke dumps in more gasoline because not all of it vaporizes, when an engine block is cold the compression is also lower due to larger ring gap and so on.
I'm not saying that warm fuel will not work, but it's going to be fussy, keep it warm for to long or keep it to warm and you can cook it down to varnish that will not burn, it just seems like a whole block heater is going to do a better job and make the car run better from the start.

Makes sense. I have a 750W circulating coolant heater kicking around. I should probably install it, hey?

I shove the heat gun into the primaries and turn it on low and it usually fires right up. I do that on mornings where its nearing teens or less.

When I build the engine for my car I plan to use a block heater.

So by blasting hot air into the primaries, you are heating not only the carb, but the air in the manifold, and most likely the combustion chamber too, so Ryland's comments above are correct.

But this leads me to another idea. Why not install a 12V intake heater much like many diesel engines have? Many have a +grid heater right in the intake manifold or close by to pre-heat intake air before you start them up. They also continue to heat for a little while after startup. They are high capacity heaters, using 60 amps or so. I am thinking that maybe a small one in the airbox, pre-carb, would work well.

there is really no way to get a vehicle, especially a carbed one warm in 4 miles. get yourself a nice bike.

I live in Vancouver. Riding to work is coasting. Riding home is up a giant hill. Plus, I work evenings every few weeks. And it rains every single day from November to March.

I do bike a few times a week in Summer. In Winter? No thanks.