You didn't bother to list the truck model, engine size, type of transmission, type of fuel injection system, two or four-wheel-drive, or options, so there's no way to know what combination of Engine Computer, Air Bag Computer, Anti-lock Brake Computer, Body Computer, Remote Keyless Entry Computer, Anti-Theft Computer, or Automatic Load-Leveling Computer you have. All of them talk back and forth to each other on the data buss, and they all need information from the Engine Computer to do what they do. The instrument cluster is another computer module. Everything on it runs on digital signals that come from those other computers. For example, the vehicle speed sensor sends its signal to the Engine Computer, Air Bag Computer, and ABS Computer. It's usually the Engine Computer that sends the vehicle speed information to the instrument cluster. If you eliminate the Engine Computer, how will the instrument cluster know vehicle speed? On some models the speed signal goes to the instrument cluster, then that one tells vehicle speed to the other computers that need that information.
The Engine Computer also knows engine temperature. On most trucks that is another digital signal sent to the instrument cluster.
You didn't say why you're trying to do this modification. If it's just to bypass a problem with the fuel injection system, you're WAY better off having a professional diagnose and repair the problem. Even if you are able to bolt a carburetor to the engine, they can only be close to perfect fuel / air mixture at idle and at high speed. Electronic fuel injection fuel / air mixture is perfect at any engine speed, any load, any air temperature, any coolant temperature, and any barometric pressure. The only way a carburetor can give you better fuel mileage is to be set to run too lean. That will lead to increased emissions, potentially burned intake valves, and annoying hesitations and stumbles. In the mid-range, all carburetors run a little rich to avoid dropping into a lean condition and these running problems. Running rich wastes fuel as the trade-off for running smooth.
You also have to consider that carburetors can only handle about three to four pounds of fuel pressure from a mechanical pump. Most GM fuel injection systems run on more than 50 pounds of fuel pressure. That will blow a carburetor's float to kingdom come.
Your transmission will have a lock-up torque converter for better fuel mileage and reduced transmission temperature. That won't work with no signals coming from the Engine Computer. Even if you try to leave the Engine Computer connected, it is going to go wild with diagnostic fault codes. When codes are set, the computer suspends some of its operations and things it controls. You'll need to use a distributor for spark and ignition timing advance.
One more thing most of us forget about is gasoline today is really terrible. The ethanol in it is very corrosive and will usually destroy the rubber seals and diaphragms. Just ask Jay Leno about all the problems he's having with his fleet of cars with carburetors. You'll need to buy ethanol-free gas which is always more expensive, assuming you can find it.
Everyone here knows I really hate all the insane engineers at all the manufacturers for their ridiculous over-use of unnecessary, unreliable, complicated, and expensive technology for systems that have been around for decades but never needed a computer before, but as a hater of "inappropriate" use of technology, I would never want to go back to a carburetor. I don't mind being bothered to have to tap the accelerator pedal to prime a carburetor for starting, and I certainly would prefer to not need high-failure sensors to trigger injector and ignition coil timing, but when you consider that today you can suck on a tail pipe and live to tell about it, and in spite of the likelihood of an electrical failure, today's vehicles are pretty certain to get you back home, even I am happy to have an Engine Computer in most of my vehicles.
The only reasons I can surmise you want to perform this modification is you're building a truck to race or you don't understand how to diagnose a problem. As a former amateur racer myself, I can tell you I didn't have much time to study the gauges. You can install aftermarket gauges for that.
If you're doing this because you don't know how to diagnose a problem, join the crowd. None of us know everything about every system, but for every system, there are plenty of experts around who DO understand them. If you post a bunch of additional information related to the things I brought up, I might be able to provide a better answer for you. If you want to diagnose a problem you're having with the fuel injection system, there are a couple of other, really good experts here I can get involved on your behalf.
Wednesday, March 11th, 2015 AT 11:14 PM