I will take the distributor out tomorrow and inspect I also know dad and my brother put the number one on top dead centr and unplugged the plug and it still ran like hell that's why we think it's the gears

 

mv7fd,

Welcome to the forum! These 1984-1986 4.9L engines are originally equipped to be controlled by a computer. The system is often referred to as a "feedback system". The carburetor and distributor are controlled by the computer. The computer gets information from temperature sensors, a MAP sensor as well as an O2 sensor mounted in the exhaust manifold. There are MANY vacuum hoses, some of them a hard plastic, which is prone to cracking after 25+ years of high temperature and vibration. Also, the carburetors are known to loosen at the base due to engine vibration. If any of these items are loose or malfunctioning, the truck will run poorly.

If a previous owner has disabled any of the emmission system components, the computer will go into a "safe" or "limp home" mode. The ignition timing will be locked, the carburetor will be set to run rich and performance will be awful and gas mileage will be terrible.

You might consider looking at the easy stuff first and make sure all is well.

By the way, have you checked spark plugs, plug wires, distributor cap and rotor, fuel filter as well as air filter?

Look at your distributor. Does it have a bunch of wires connected at the base or does it have a vacuum canister?

Good luck.