Sounds like timing.
Have you ever seen this truck run?
Is you fuel new or old?
Is your exhaust open or clogged or bent?
I think some more diagnosis is ness. Pull out #1 plug, with a long thin screwdriver stuck in the hole use a wrench to turn over the engine untill you feel the piston move the screwdriver. When the piston moves the screwdriver to the top of the piston stroke (TDC or top dead center) look in the hole just above and to the rt. of the starter. This is the timing hole. Inside the hole you should see a ball emdeded into the flywheel or a line cut into the flywheel. If you don't see the ball or line, move the crankshaft with a wrench an inch in both directions untill you see the ball or line. With the ball or line in view remove the distributor cap and watch the rotor,with your wrench move the crankshaft untill the rotor begins to move and stop. Now make a mental note of where the ball or line is positioned in the hole. With your wrench move the crankshaft the oppisite direction and look for the rotor to move and then stop and look at the ball or line. Did the ball or line move more than 1/2 inch before the rotor turned? If it did you have timing gear or chain problems. If not put the plug back in and move the distributor as someone else spins it over and try to start the truck. If you rule out all other possibilities of spark, fuel,compression,and timing unbolt the exhaust and try to start it again. It might just be restricted. Good luck

I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"