The "original" choke for your truck will never work right with the BBD carburetor. I strongly recommend you get the CarbsOnly kit.
If you are serious about improving your fuel economy, then you must install at the very least a vacuum gauge and a tachometer. You will also have to determine basics like your rear axle gear ratio, what kind of transmission you have (three or four speed, etc...) If you are trying to keep the truck looking like an original vintage 60s truck, then you can track down period correct or reproduction of period correct gauges. Without proper instrumentation you will never be able to accurately document what is going on with your motor and make improvements.
As far as the tires go, wider tires cause more rolling resistance. Skinnier tires give better fuel economy. If you do go back to skinnier tires, I strongly recommend you get light truck tires. They have stiffer sidewalls that will help with the "wishy-washy" feeling.
Jacking up both wheels will never be the right way to find out the rear gear ratio since the wheels will just spin freely. Since you need to learn what kind of rear end you have anyway, I recommend either pulling the rear differential cover or dropping the center carrier and counting the gears.
The cold and hot air intake systems can and were used together, and both are good to have. The heated air intake operates only when the ambient temperature is very cold- typically below freezing but there was some variation. There is a sensor mounted inside the air cleaner that senses the temperature of the air entering the air cleaner. This sensor controls a vacuum switch. When the air is cold enough, vacuum from the carb is applied to an actuator in the air cleaner snorkel which opens the flap in the floor of the snorkel and allows hot air drawn from around the exhaust pipe to be drawn into the intake. This helps with cold-weather driveability and with cold-startups. Once the ambient air in the air cleaner gets above a certain temperature, the sensor blocks vacuum flow to the flap in the snorkel and the door closes, blocking the hot air from entering.
A cold air intake is nothing more than a hose from the end of the air cleaner snorkel out to some spot behind the grille or in one of the fender wells which allows the carburetor to suck colder air from outside the engine compartment. It is a long-knwon and well documented fact that motors give better performance and fuel economy when they draw in cooler air (the caveat to this is when the motor is first starting up in cold weather, which is why heated air intake systems were used). On older cars and trucks (basically mid 70s and older, except for some exceptions), stock air cleaners were designed to draw the air for the engine from the engine bay. This meant that the carb was constantly fed hot air. Adding a cold air intake feeds the carb cooler denser air and improved fuel economy and performance.
Both heated and cold air intake systems were used by all manufacturers by the early 80s, some even earlier. Chrysler cars got them starting around 76 or 77, and trucks got them by the early 80s. I highly recommend you add a cold air intake to your truck.
You fuel economy will be greatly impacted by the gears in your truck as well as the ignition system, timing advance curve, and driving style.
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