[dmjlambert]

I suggest use a thin wire, such as a 28 or 30 gauge wire, strip the end and put it over the terminal on the distributor coil and push the connector onto it. Then run that wire into the cab and connect it to a voltmeter that you can view while driving. You can find out if you lose voltage right at the point where the electricity goes into the coil. If it dies while driving, look at the meter and see if you still have electricity there.

It sounds like you may have an electric fuel pump. Repeat the test for the fuel pump by checking that you have electricity at the fuel pump when it dies. If the fuel pump has a separate wire going to it for ground, connect the volt meter across both wires of the fuel pump, so you can know your pump is powered. There may be an oil pressure switch that allows the fuel pump to run only if the engine is turning, or another type of safety shut off that is causing the problem.