Just to make sure the ignition timing is right, try this little trick: Pull the valve cover, and watch the rocker arms on #6 cylinder, not #1. Roll the engine over slowly by putting the transmission in 3rd gear, and pushing the truck forward until the #6 exhaust valve opens (last rocker arm in line). Continue rolling the engine over until the exhaust closes, and the intake just begins to open.
At that point, the #1 cylinder will be on top of the compression stroke, ready to fire the spark plug. The distributor rotor should be pointing at the #1 plug connector in the distributor cap. If it's pointing anywhere else, you're out of time! Now, turn the distributor housing clockwise until the points close, then turn it back counterclockwise until they just barely open. The ignition timing will be within a couple of degrees of the correct setting.
Try a NEW, not cleaned-up set of spark plugs. I've seen new-looking plugs get fuel-soaked, and they never fire again! Good luck!
Jerry
