Truck wont stay running

I'm going to try and answer this with the best of my general car knowledge, unfortunately, I've never owned/fixed a Dodge Ram, but in my opinion if you can fix one car, you can fix them all. If you don't own a service manual for your car and want to troubleshoot this yourself, buy/borrow one, it's an incredibly valuable tool. If the engine was overhauled/rebuilt, then the problem it probably with the air intake, vacuum system, or exhaust system and not the engine itself. Is the check engine light on? Reading that with a code-scanner could give you valuable information about the problem. Some auto part stores will scan your car for free. If you have no check engine light, the problem probably lies with the 3 systems I listed, and you will need to troubleshoot this yourself or take it to a mechanic. First start with the vacuum system, as this is the easiest to troubleshoot. It's possible that a vacuum line may have been damaged during the engine overhaul. This video details the process pretty well. You can also listen for vacuum leaks, vacuum lines are usually black hoses >1cm in diameter, they run around different parts towards the top of the engine, and make a pretty distinctive hiss when they are leaking. The next step would be to check the air intake. Chances are, when your engine was rebuilt, the intake manifold was inspected and it's gaskets replaced. That leaves the throttle body, which may need to be cleaned. Use your service manual to remove the hose that goes into the throttle body, this video shows how to clean it. The last step is to check the exhaust system, this probably isn't the problem as sensors in modern exhaust systems will detect a problem with flow. Listen to the exhaust system while the car is running near the catalytic converter (the bulge in the exhaust pipe behind his hand), when this fails it breaks apart and can cause the exhaust pipe to clog. If troubleshooting these things doesn't fix the car, you may need to take it to a mechanic. Good Luck!